First American Financial Pays Farcical $500K Fine

June 18, 2021
37 Comments

In May 2019, KrebsOnSecurity broke the news that the website of mortgage settlement giant First American Financial Corp. [NYSE:FAF] was leaking more than 800 million documents — many containing sensitive financial data — related to real estate transactions dating back 16 years. This week, the U.S. Securities and Exchange Commission settled its investigation into the matter after the Fortune 500 company agreed to pay a paltry penalty of less than $500,000.

First American Financial Corp.

If you bought or sold a property in the last two decades or so, chances are decent that you also gave loads of personal and financial documents to First American. According to data from the American Land Title Association, First American is the second largest mortgage title and settlement company in the United States, handling nearly a quarter of all closings each year.

The SEC says First American derives nearly 92 percent of its revenue from its title insurance segment, earning $7.1 billion last year.

Title insurance protects homebuyers from the prospect of someone contesting their legitimacy as the new homeowner. According to SimpleShowing.com, there are actually two title insurance policies in each transaction — one for the buyer and one for the lender (the latter also needs protection as they’re providing the mortgage to purchase the home).

Title insurance is not mandated by law, but most lenders require it as part of any mortgage transaction. In other words, if you wish to take out a mortgage on a home you will not be able to do so without giving companies like First American gobs of documents about your income, assets and liabilities — including quite a bit of sensitive financial data.

Aside from its core business competency — checking to make sure the property at issue in any real estate transaction is unencumbered by any liens or other legal claims against it — First American basically has one job: Protect the privacy and security of all these documents.

A redacted screenshot of one of many millions of sensitive records exposed by First American’s Web site.

It’s easy to see why companies like First American might not view protecting this data as sacrosanct, as the entire industry’s incentive for safeguarding all those sensitive documents is somewhat misaligned.

That is to say, in the title insurance industry the parties to a real estate transaction aren’t customers, but rather they are are the product. The actual customers of the title insurance companies are principally the banks which back these mortgage transactions.

We see a similar dynamic with social media platforms, where the “user” is not the customer at all but the product whose data is being bought and sold by these platforms.

Roughly five months before KrebsOnSecurity notified First American that anyone with a web browser could view sensitive document in its “Eagle Pro” database online just by changing some characters at the end of a link, an internal security audit at First American flagged the exact same vulnerability.

But the company never acted to fix it until the news media came calling. Continue reading →

Ukrainian Police Nab Six Tied to CLOP Ransomware

June 16, 2021
31 Comments

Authorities in Ukraine this week charged six people alleged to be part of the CLOP ransomware group, a cybercriminal gang said to have extorted more than half a billion dollars from victims. Some of CLOP’s victims this year alone include Stanford University Medical School, the University of California, and University of Maryland.

A still shot from a video showing Ukrainian police seizing a Tesla, one of many high-end vehicles seized in this week’s raids on the Clop gang.

According to a statement and videos released today, the Ukrainian Cyber Police charged six defendants with various computer crimes linked to the CLOP gang, and conducted 21 searches throughout the Kyiv region.

First debuting in early 2019, CLOP is one of several ransomware groups that hack into organizations, launch ransomware that encrypts files and servers, and then demand an extortion payment in return for a digital key needed to unlock access.

/

CLOP has been especially busy over the past six months exploiting four different zero-day vulnerabilities in File Transfer Appliance (FTA), a file sharing product made by California-based Accellion.

The CLOP gang seized on those flaws to deploy ransomware to a significant number of Accellion’s FTA customers, including U.S. grocery chain Krogers, the law firm Jones Day, security firm Qualys, and the Singaporean telecom giant Singtel.

Last year, CLOP adopted the practice of attempting to extract a second ransom demand from victims in exchange for a promise not to publish or sell any stolen data. Terabytes of documents and files stolen from victim organizations that have not paid a data ransom are now available for download from CLOP’s deep web site, including Stanford, UCLA and the University of Maryland.

CLOP’s victim shaming blog on the deep web.

Continue reading →

Advertisement

How Does One Get Hired by a Top Cybercrime Gang?

June 15, 2021
38 Comments

The U.S. Department of Justice (DOJ) last week announced the arrest of a 55-year-old Latvian woman who’s alleged to have worked as a programmer for Trickbot, a malware-as-a-service platform responsible for infecting millions of computers and seeding many of those systems with ransomware.

Just how did a self-employed web site designer and mother of two come to work for one of the world’s most rapacious cybercriminal groups and then leave such an obvious trail of clues indicating her involvement with the gang? This post explores answers to those questions, as well as some of the ways Trickbot and other organized cybercrime gangs gradually recruit, groom and trust new programmers.

Alla Witte’s personal website — allawitte[.]nl — circa October 2018.

The indictment released by the DOJ (PDF) is heavily redacted, and only one of the defendants is named: Alla “Max” Witte, a 55-year-old Latvian national who was arrested Feb. 6 in Miami, Fla.

The DOJ alleges Witte was responsible for “overseeing the creation of code related to the monitoring and tracking of authorized users of the Trickbot malware, the control and deployment of ransomware, obtaining payments from ransomware victims, and developing tools and protocols for the storage of credentials stolen and exfiltrated from victims infected by Trickbot.”

The indictment also says Witte provided code to the Trickbot Group for a web panel used to access victim data stored in a database. According to the government, that database contained a large number of credit card numbers and stolen credentials from the Trickbot botnet, as well as information about infected machines available as bots.

“Witte provided code to this repository that showed an infected computer or ‘bot’ status in different colors based on the colors of a traffic light and allowed other Trickbot Group members to know when their co-conspirators were working on a particular infected machine,” the indictment alleges.

While any law enforcement action against a crime group that has targeted hospitals, schools, public utilities and governments is good news, Witte’s indictment and arrest were probably inevitable: It is hard to think of an accused cybercriminal who has made more stunningly poor and rookie operational security mistakes than this Latvian senior citizen.

For starters, it appears at one point in 2020 Witte actually hosted Trickbot malware on a vanity website registered in her name — allawitte[.]nl.

While it is generally a bad idea for cybercriminals to mix their personal life with work, Witte’s social media accounts mention a close family member (perhaps her son or husband) had the first name “Max,” which allegedly was her hacker handle.

Unlike many accused cybercriminals who hail from Russia or former Soviet countries, Witte did not feel obligated to avoid traveling to areas where she might be within reach of U.S. law enforcement agencies. According to her indictment, Witte was living in the South American nation of Suriname and she was arrested in Miami while flying from Suriname. It is not clear where her intended destination was.

A Google-translated post Witte made to her Vkontakte page, five years before allegedly joining the Trickbot group.

Alex Holden, founder of the cybersecurity intelligence firm Hold Security, said Witte’s greatest lapse in judgment came around Christmas time in 2019, when she infected one of her own computers with the Trickbot malware — allowing it to steal and log her data within the botnet interface.

“On top of the password re-use, the data shows a great insight into her professional and personal Internet usage,” Holden wrote in a blog post on Witte’s arrest.

“Many in the gang not only knew her gender but her name too,” Holden wrote. “Several group members had AllaWitte folders with data. They refer to Alla almost like they would address their mothers.”

So how did this hacker mom with apparently zero sense of self-preservation come to work for one of the world’s most predatory cybercriminal gangs? Continue reading →

Microsoft Patches Six Zero-Day Security Holes

June 8, 2021
59 Comments

Microsoft today released another round of security updates for Windows operating systems and supported software, including fixes for six zero-day bugs that malicious hackers already are exploiting in active attacks.

June’s Patch Tuesday addresses just 49 security holes — about half the normal number of vulnerabilities lately. But what this month lacks in volume it makes up for in urgency: Microsoft warns that bad guys are leveraging a half-dozen of those weaknesses to break into computers in targeted attacks.

Among the zero-days are:

–CVE-2021-33742, a remote code execution bug in a Windows HTML component.
–CVE-2021-31955, an information disclosure bug in the Windows Kernel
–CVE-2021-31956, an elevation of privilege flaw in Windows NTFS
–CVE-2021-33739, an elevation of privilege flaw in the Microsoft Desktop Window Manager
–CVE-2021-31201, an elevation of privilege flaw in the Microsoft Enhanced Cryptographic Provider
–CVE-2021-31199, an elevation of privilege flaw in the Microsoft Enhanced Cryptographic Provider

Kevin Breen, director of cyber threat research at Immersive Labs, said elevation of privilege flaws are just as valuable to attackers as remote code execution bugs: Once the attacker has gained an initial foothold, he can move laterally across the network and uncover further ways to escalate to system or domain-level access.

“This can be hugely damaging in the event of ransomware attacks, where high privileges can enable the attackers to stop or destroy backups and other security tools,” Breen said. “The ‘exploit detected’ tag means attackers are actively using them, so for me, it’s the most important piece of information we need to prioritize the patches.” Continue reading →

Justice Dept. Claws Back $2.3M Paid by Colonial Pipeline to Ransomware Gang

June 7, 2021
238 Comments

The U.S. Department of Justice said today it has recovered $2.3 million worth of Bitcoin that Colonial Pipeline paid to ransomware extortionists last month. The funds had been sent to DarkSide, a ransomware-as-a-service syndicate that disbanded after a May 14 farewell message to affiliates saying its Internet servers and cryptocurrency stash were seized by unknown law enforcement entities.

On May 7, the DarkSide ransomware gang sprang its attack against Colonial, which ultimately paid 75 Bitcoin (~$4.4 million) to its tormentors. The company said the attackers only hit its business IT networks — not its pipeline security and safety systems — but that it shut the pipeline down anyway as a precaution [several publications noted Colonial shut down its pipeline because its billing system was impacted, and it had no way to get paid].

On or around May 14, the DarkSide representative on several Russian-language cybercrime forums posted a message saying the group was calling it quits.

“Servers were seized, money of advertisers and founders was transferred to an unknown account,” read the farewell message. “Hosting support, apart from information ‘at the request of law enforcement agencies,’ does not provide any other information.”

A message from the DarkSide and REvil ransomware-as-a-service cybercrime affiliate programs.

Many security experts said they suspected DarkSide was just laying low for a while thanks to the heat from the Colonial attack, and that the group would re-emerge under a new banner in the coming months. And while that may be true, the seizure announced today by the DOJ certainly supports the DarkSide administrator’s claims that their closure was involuntary.

Security firms have suspected for months that the DarkSide gang shares some leadership with that of REvil, a.k.a. Sodinokibi, another ransomware-as-a-service platform that closed up shop in 2019 after bragging that it had extorted more than $2 billion from victims. That suspicion was solidified further when the REvil administrator added his comments to the announcement about DarkSide’s closure (see screenshot above).

First surfacing on Russian language hacking forums in August 2020, DarkSide is a ransomware-as-a-service platform that vetted cybercriminals can use to infect companies with ransomware and carry out negotiations and payments with victims. DarkSide says it targets only big companies, and forbids affiliates from dropping ransomware on organizations in several industries, including healthcare, funeral services, education, public sector and non-profits.

According to an analysis published May 18 by cryptocurrency security firm Elliptic, 47 cybercrime victims paid DarkSide a total of $90 million in Bitcoin, putting the average ransom payment of DarkSide victims at just shy of $2 million. Continue reading →

Adventures in Contacting the Russian FSB

June 7, 2021
39 Comments

KrebsOnSecurity recently had occasion to contact the Russian Federal Security Service (FSB), the Russian equivalent of the U.S. Federal Bureau of Investigation (FBI). In the process of doing so, I encountered a small snag: The FSB’s website said in order to communicate with them securely, I needed to download and install an encryption and virtual private networking (VPN) appliance that is flagged by at least 20 antivirus products as malware.

The FSB headquarters at Lubyanka Square, Moscow. Image: Wikipedia.

The reason I contacted the FSB — one of the successor agencies to the Russian KGB — ironically enough had to do with security concerns raised by an infamous Russian hacker about the FSB’s own preferred method of being contacted.

KrebsOnSecurity was seeking comment from the FSB about a blog post published by Vladislav “BadB” Horohorin, a former international stolen credit card trafficker who served seven years in U.S. federal prison for his role in the theft of $9 million from RBS WorldPay in 2009. Horohorin, a citizen of Russia, Israel and Ukraine, is now back where he grew up in Ukraine, running a cybersecurity consulting business.

Horohorin’s BadB carding store, badb[.]biz, circa 2007. Image: Archive.org.

Visit the FSB’s website and you might notice its web address starts with http:// instead of https://, meaning the site is not using an encryption certificate. In practical terms, any information shared between the visitor and the website is sent in plain text and will be visible to anyone who has access to that traffic.

This appears to be the case regardless of which Russian government site you visit. According to Russian search giant Yandex, the laws of the Russian Federation demand that encrypted connections be installed according to the Russian GOST cryptographic algorithm.

That means those who have a reason to send encrypted communications to a Russian government organization — including ordinary things like making a payment for a government license or fine, or filing legal documents — need to first install CryptoPro, a Windows-only application that loads the GOST encryption libraries on a user’s computer.

But if you want to talk directly to the FSB over an encrypted connection, you can just install their own client, which bundles the CryptoPro code. Visit the FSB’s site and select the option to “transfer meaningful information to operational units,” and you’ll see a prompt to install a “random number generation” application that is needed before a specific contact form on the FSB’s website will load properly.

Mind you, I’m not suggesting anyone go do that: Horohorin pointed out that this random number generator was flagged by 20 different antivirus and security products as malicious.

“Think well before contacting the FSB for any questions or dealing with them, and if you nevertheless decide to do this, it is better to use a virtual machine,” Horohorin wrote. “And a spacesuit. And, preferably, while in another country.”

Antivirus product detections on the FSB’s VPN software. Image: VirusTotal.

It’s probably worth mentioning that the FSB is the same agency that’s been sanctioned for malicious cyber activity by the U.S. government on multiple occasions over the past five years. According to the most recent sanctions by the U.S. Treasury Department, the FSB is known for recruiting criminal hackers from underground forums and offering them legal cover for their actions.

“To bolster its malicious cyber operations, the FSB cultivates and co-opts criminal hackers, including the previously designated Evil Corp., enabling them to engage in disruptive ransomware attacks and phishing campaigns,” reads a Treasury assessment from April 2021.

While Horohorin seems convinced the FSB is disseminating malware, it is not unusual for a large number of security tools used by VirusTotal or other similar malware “sandbox” services to incorrectly flag safe files as bad or suspicious — an all-too-common condition known as a “false positive.”

Late last year I warned my followers on Twitter to put off installing updates for their Dell products until the company could explain why a bunch of its software drivers were being detected as malware by two dozen antivirus tools. Those all turned out to be false positives.

To really figure out what this FSB software was doing, I turned to Lance James, the founder of Unit221B, a New York City based cybersecurity firm. James said each download request generates a new executable program. That is because the uniqueness of the file itself is part of what makes the one-to-one encrypted connection possible. Continue reading →

Using Fake Reviews to Find Dangerous Extensions

May 29, 2021
39 Comments

Fake, positive reviews have infiltrated nearly every corner of life online these days, confusing consumers while offering an unwelcome advantage to fraudsters and sub-par products everywhere. Happily, identifying and tracking these fake reviewer accounts is often the easiest way to spot scams. Here’s the story of how bogus reviews on a counterfeit Microsoft Authenticator browser extension exposed dozens of other extensions that siphoned personal and financial data.

Comments on the fake Microsoft Authenticator browser extension show the reviews for these applications are either positive or very negative — basically calling it out as a scam. Image: chrome-stats.com.

After hearing from a reader about a phony Microsoft Authenticator extension that appeared on the Google Chrome Store, KrebsOnSecurity began looking at the profile of the account that created it. There were a total of five reviews on the extension before it was removed: Three Google users gave it one star, warning people to stay far away from it; but two of the reviewers awarded it between three and four stars.

“It’s great!,” the Google account Theresa Duncan enthused, improbably. “I’ve only had very occasional issues with it.”

“Very convenient and handing,” assessed Anna Jones, incomprehensibly.

Google’s Chrome Store said the email address tied to the account that published the knockoff Microsoft extension also was responsible for one called “iArtbook Digital Painting.” Before it was removed from the Chrome Store, iArtbook had garnered just 22 users and three reviews. As with the knockoff Microsoft extension, all three reviews were positive, and all were authored by accounts with first and last names, like Megan Vance, Olivia Knox, and Alison Graham.

Google’s Chrome Store doesn’t make it easy to search by reviewer. For that I turned to Hao Nguyen, the developer behind chrome-stats.com, which indexes and makes searchable a broad array of attributes about extensions available from Google.

Looking at the Google accounts that left positive reviews on both the now-defunct Microsoft Authenticator and iArtbook extensions, KrebsOnSecurity noticed that each left positive reviews on a handful of other extensions that have since been removed.

Reviews on the iArtbook extension were all from apparently fake Google accounts that each reviewed two other extensions, one of which was published by the same developer. This same pattern was observed across 45 now-defunct extensions.

Like an ever-expanding venn diagram, a review of the extensions commented on by each new fake reviewer found led to the discovery of even more phony reviewers and extensions. In total, roughly 24 hours worth of digging through chrome-stats.com unearthed more than 100 positive reviews on a network of patently fraudulent extensions.

Those reviews in turn lead to the relatively straightforward identification of:

-39 reviewers who were happy with extensions that spoofed major brands and requested financial data
-45 malicious extensions that collectively had close to 100,000 downloads
-25 developer accounts tied to multiple banned applications

The extensions spoofed a range of consumer brands, including Adobe, Amazon, Facebook, HBO, Microsoft, Roku and Verizon. Scouring the manifests for each of these other extensions in turn revealed that many of the same developers were tied to multiple apps being promoted by the same phony Google accounts.

Some of the fake extensions have only a handful of downloads, but most have hundreds or thousands. A fake Microsoft Teams extension attracted 16,200 downloads in the roughly two months it was available from the Google store. A counterfeit version of CapCut, a professional video editing software suite, claimed nearly 24,000 downloads over a similar time period.

More than 16,000 people downloaded a fake Microsoft Teams browser extension over the roughly two months it was available for download from the Google Chrome store.

Unlike malicious browser extensions that can turn your PC into a botnet or harvest your cookies, none of the extensions examined here request any special permissions from users. Once installed, however, they invariably prompt the user to provide personal and financial data — all the while pretending to be associated with major brand names. Continue reading →

Boss of ATM Skimming Syndicate Arrested in Mexico

May 28, 2021
22 Comments

Florian “The Shark” Tudor, the alleged ringleader of a prolific ATM skimming gang that siphoned hundreds of millions of dollars from bank accounts of tourists visiting Mexico over the last eight years, was arrested in Mexico City on Thursday in response to an extradition warrant from a Romanian court.

Florian Tudor, at a 2020 press conference in Mexico in which he asserted he was a legitimate businessman and not a mafia boss. Image: OCCRP.

Tudor, a native of Craiova, Romania, moved to Mexico to set up Top Life Servicios, an ATM servicing company which managed a fleet of relatively new ATMs based in Mexico branded as Intacash.

Intacash was the central focus of a three–part investigation KrebsOnSecurity published in September 2015. That series tracked the activities of a crime gang working with Intacash that was bribing and otherwise coercing ATM technicians to install sophisticated Bluetooth-based skimmers inside cash machines throughout popular tourist destinations in and around Mexico’s Yucatan Peninsula — including Cancun, Cozumel, Playa del Carmen and Tulum.

Follow-up reporting last year by the Organized Crime and Corruption Reporting Project (OCCRP) found Tudor and his associates compromised more than 100 ATMs across Mexico using skimmers that were able to remain in place undetected for years. The OCCRP, which dubbed Tudor’s group “The Riviera Maya Gang,” estimates the crime syndicate used cloned card data and stolen PINs to steal more than $1.2 billion from bank accounts of tourists visiting the region.

Last year, a Romanian court ordered Tudor’s capture following his conviction in absentia for attempted murder, blackmail and the creation of an organized crime network that specialized in human trafficking.

Mexican authorities have been examining bank accounts tied to Tudor and his companies, and investigators believe Tudor and his associates paid protection and hush money to various Mexican politicians and officials over the years. In February, the leader of Mexico’s Green Party stepped down after it emerged that he received funds from Tudor’s group.

This is the second time Mexican authorities have detained Tudor. In April 2019, Tudor and his deputy were arrested for illegal firearms possession. That arrest came just months after Tudor allegedly ordered the execution of a former bodyguard who was trying to help U.S. authorities bring down the group’s lucrative skimming operations.

Tudor’s arrest this week inside the premises of the Mexican Attorney General’s Office did not go smoothly, according to Mexican news outlets. El Universal reports that a brawl broke out between Tudor’s lawyers and officials at the Mexican AG’s office, and a video released by the news outlet on Twitter shows Tudor resisting arrest as he is being hauled out of the building hand and foot.

A Mexican judge will decide on Tudor’s extradition to Romania in the coming weeks.

How to Tell a Job Offer from an ID Theft Trap

May 21, 2021
57 Comments

One of the oldest scams around — the fake job interview that seeks only to harvest your personal and financial data — is on the rise, the FBI warns. Here’s the story of a recent LinkedIn impersonation scam that led to more than 100 people getting duped, and one almost-victim who decided the job offer was too-good-to-be-true.

Last week, someone began posting classified notices on LinkedIn for different design consulting jobs at Geosyntec Consultants, an environmental engineering firm based in the Washington, D.C. area. Those who responded were told their application for employment was being reviewed and that they should email Troy Gwin — Geosyntec’s senior recruiter — immediately to arrange a screening interview.

Gwin contacted KrebsOnSecurity after hearing from job seekers trying to verify the ad, which urged respondents to email Gwin at a Gmail address that was not his. Gwin said LinkedIn told him roughly 100 people applied before the phony ads were removed for abusing the company’s terms of service.

“The endgame was to offer a job based on successful completion of background check which obviously requires entering personal information,” Gwin said. “Almost 100 people applied. I feel horrible about this. These people were really excited about this ‘opportunity’.”

Erica Siegel was particularly excited about the possibility of working in a creative director role she interviewed for at the fake Geosyntec. Siegel said her specialty —  “consulting with start ups and small businesses to create sustainable fashion, home and accessories brands” — has been in low demand throughout the pandemic, so she’s applied to dozens of jobs and freelance gigs over the past few months.

On Monday, someone claiming to work with Gwin contacted Siegel and asked her to set up an online interview with Geosyntec. Siegel said the “recruiter” sent her a list of screening questions that all seemed relevant to the position being advertised.

Siegel said that within about an hour of submitting her answers, she received a reply saying the company’s board had unanimously approved her as a new hire, with an incredibly generous salary considering she had to do next to no work to get a job she could do from home.

Worried that her potential new dream job might be too-good-to-be-true, she sent the recruiter a list of her own questions that she had about the role and its position within the company.

But the recruiter completely ignored Siegel’s follow-up questions, instead sending a reply that urged her to get in touch with a contact in human resources to immediately begin the process of formalizing her employment. Which of course involves handing over one’s personal (driver’s license info) and financial details for direct deposit.

Multiple things about this job offer didn’t smell right to Siegel.

“I usually have six or seven interviews before getting a job,” Siegel said. “Hardly ever in my lifetime have I seen a role that flexible, completely remote and paid the kind of money I would ask for. You never get all three of those things.”

So she called her dad, an environmental attorney who happens to know and have worked with people at the real Geosyntec Consultants. Then she got in touch with the real Troy Gwin, who confirmed her suspicions that the whole thing was a scam.

“Even after the real Troy said they’d gotten these [LinkedIn] ads shut down, this guy was still emailing me asking for my HR information,” Siegel said. “So my dad said, ‘Troll him back, and tell him you want a signing bonus via money order.’ I was like, okay, what’s the worst that could happen? I never heard from him again.” Continue reading →

Recycle Your Phone, Sure, But Maybe Not Your Number

May 19, 2021
37 Comments

Many online services allow users to reset their passwords by clicking a link sent via SMS, and this unfortunately widespread practice has turned mobile phone numbers into de facto identity documents. Which means losing control over one thanks to a divorce, job termination or financial crisis can be devastating.

Even so, plenty of people willingly abandon a mobile number without considering the potential fallout to their digital identities when those digits invariably get reassigned to someone else. New research shows how fraudsters can abuse wireless provider websites to identify available, recycled mobile numbers that allow password resets at a range of email providers and financial services online.

Researchers in the computer science department at Princeton University say they sampled 259 phone numbers at two major wireless carriers, and found 171 of them were tied to existing accounts at popular websites, potentially allowing those accounts to be hijacked.

The Princeton team further found 100 of those 259 numbers were linked to leaked login credentials on the web, which could enable account hijackings that defeat SMS-based multi-factor authentication.

“Our key finding is that attackers can feasibly leverage number recycling to target previous owners and their accounts,” the researchers wrote. “The moderate to high hit rates of our testing methods indicate that most recycled numbers are vulnerable to these attacks. Furthermore, by focusing on blocks of Likely recycled numbers, an attacker can easily discover available recycled numbers, each of which then becomes a potential target.”

The researchers located newly-recycled mobile numbers by browsing numbers made available to customers interested in signing up for a prepaid account at T-Mobile or Verizon (apparently AT&T doesn’t provide a similar interface). They said they were able to identify and ignore large blocks of new, unused numbers, as these blocks tend to be made available consecutively — much like newly printed money is consecutively numbered in stacks.

The Princeton team has a number of recommendations for T-Mobile and Verizon, noting that both carriers allow unlimited inquiries on their prepaid customer platforms online — meaning there is nothing to stop attackers from automating this type of number reconnaissance.

“On postpaid interfaces, Verizon already has safeguards and T-Mobile does not even support changing numbers online,” the researchers wrote. “However, the number pool is shared between postpaid and prepaid, rendering all subscribers vulnerable to attacks.” Continue reading →