Posts Tagged: gmail

Sep 16

The Limits of SMS for 2-Factor Authentication

A recent ping from a reader reminded me that I’ve been meaning to blog about the security limitations of using cell phone text messages for two-factor authentication online. The reader’s daughter had received a text message claiming to be from Google, warning that her Gmail account had been locked because someone in India had tried to access her account. The young woman was advised to expect a 6-digit verification code to be sent to her and to reply to the scammer’s message with that code.

2faMark Cobb, a computer technician in Reno, Nev., said had his daughter fallen for the ruse, her Gmail account would indeed have been completely compromised, and she really would have been locked out of her account because the crooks would have changed her password straight away.

Cobb’s daughter received the scam text message because she’d enabled 2-factor authentication on her Gmail account, selecting the option to have Google request that she enter a 6-digit code texted to her cell phone each time it detects a login from an unknown computer or location (in practice, the code is to be entered on the Gmail site, not sent in any kind of texted or emailed reply).

In this case, the thieves already had her password — most likely because she re-used it on some other site that got hacked. Cobb says he and his daughter believe her mobile number and password may have been exposed as part of the 2012 breach at LinkedIn.

In any case, the crooks were priming her to expect a code and to repeat it back to them because that code was the only thing standing in the way of their seizing control over her account. And they could control when Google would send the code to her phone because Google would do this as soon as they tried to log in using her username and password. Indeed, the timing aspect of this attack helps make it more believable to the target.

This is a fairly clever — if not novel — attack, and it’s one I’d wager would likely fool a decent percentage of users who have enabled text messages as a form of two-factor authentication. Certainly, text messaging is far from the strongest form of 2-factor authentication, but it is better than allowing a login with nothing more than a username and password, as this scam illustrates.

Nevertheless, text messaging codes to users isn’t the safest way to do two-factor authentication, even if some entities — like the U.S. Social Security Administration and Sony’s Playstation network — are just getting around to offering two-factor via SMS.

But don’t take my word for it. That’s according to the National Institute of Standards and Technology (NIST), which recently issued new proposed digital authentication guidelines urging organizations to favor other forms of two-factor — such as time-base one-time passwords generated by mobile apps — over text messaging. By the way, NIST is seeking feedback on these recommendations.

If anyone’s interested, Sophos’s Naked Security blog has a very readable breakdown of what’s new in the NIST guidelines. Among my favorite highlights is this broad directive: Favor the user.

“To begin with, make your password policies user friendly and put the burden on the verifier when possible,” Sophos’s Chester Wisniewski writes. “In other words, we need to stop asking users to do things that aren’t actually improving security.” Like expiring passwords and making users change them frequently, for example.

Okay, so the geeks-in-chief are saying it’s time to move away from texting as a form of 2-factor authentication. And, of course, they’re right, because text messages are a lot like email, in that it’s difficult to tell who really sent the message, and the message itself is sent in plain text — i.e. is readable by anyone who happens to be lurking in the middle.

But security experts and many technology enthusiasts have a tendency to think that everyone should see the world through the lens of security, whereas most mere mortal users just want to get on with their lives and are perfectly content to use the same password across multiple sites — regardless of how many times they’re told not to do so. Continue reading →

Dec 15

Expect Phishers to Up Their Game in 2016

Expect phishers and other password thieves to up their game in 2016: Both Google and Yahoo! are taking steps to kill off the password as we know it.

passcrackNew authentication methods now offered by Yahoo! and to a beta group of Google users let customers log in just by supplying their email address, and then responding to a notification sent to their mobile device.

According to TechCrunch, Google is giving select Gmail users a password-free means of signing in. It uses a “push” notification sent to your phone that then opens an app where you approve the log-in.

The article says the service Google is experimenting with will let users sign in without entering a password, but that people can continue to use their typed password if they choose. It also says Google may still ask for your password as an additional security measure if it notices anything unusual about a login attempt.

The new authentication feature being tested by some Gmail users comes on the heels of a similar service Yahoo! debuted in October 2015. That offering, called “on-demand passwords,” will text users a random four-character code (the ones I saw were all uppercase letters) that needs to be entered into a browser or mobile device.


This is not Yahoo!’s first stab at two-factor authentication. Another security feature it has offered for years — called “two-step verification” — sends a security code to your phone when you log in from new devices, but only after you supply your password. Yahoo! users who wish to take advantage of the passwords-free, on-demand password feature will need to disable two-step verification for on-demand passwords to work.

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Aug 13

Buying Battles in the War on Twitter Spam

The success of social networking community Twitter has given rise to an entire shadow economy that peddles dummy Twitter accounts by the thousands, primarily to spammers, scammers and malware purveyors. But new research on identifying bogus accounts has helped Twitter to drastically deplete the stockpile of existing accounts for sale, and holds the promise of driving up costs for both vendors of these shady services and their customers.



Twitter prohibits the sale and auto-creation of accounts, and the company routinely suspends accounts created in violation of that policy. But according to researchers from George Mason University, the International Computer Science Institute and the University of California, Berkeley, Twitter traditionally has done so only after these fraudulent accounts have been used to spam and attack legitimate Twitter users.

Seeking more reliable methods of detecting auto-created accounts before they can be used for abuse, the researchers approached Twitter last year for the company’s blessing to purchase credentials from a variety of Twitter account merchants. Permission granted, the researchers spent more than $5,000 over ten months buying accounts from at least 27 different underground sellers.

In a report to be presented at the USENIX security conference in Washington, D.C. today, the research team details its experience in purchasing more than 121,000 fraudulent Twitter accounts of varying age and quality, at prices ranging from $10 to $200 per one thousand accounts.

The research team quickly discovered that nearly all fraudulent Twitter account merchants employ a range of countermeasures to evade the technical hurdles that Twitter erects to stymie the automated creation of new accounts.

“Our findings show that merchants thoroughly understand Twitter’s existing defenses against automated registration, and as a result can generate thousands of accounts with little disruption in availability or instability in pricing,” the paper reads. “We determine that merchants can provide thousands of accounts within 24 hours at a price of $0.02 – $0.10 per account.”


For example, to fulfill orders for fraudulent Twitter accounts, merchants typically pay third-party services to help solve those squiggly-letter CAPTCHA challenges. I’ve written here and here about these virtual sweatshops, which rely on low-paid workers in China, India and Eastern Europe who earn pennies per hour deciphering the puzzles.

topemailThe Twitter account sellers also must verify new accounts with unique email addresses, and they tend to rely on services that sell cheap, auto-created inboxes at HotmailYahoo and, the researchers found. “The failure of email confirmation as a barrier directly stems from pervasive account abuse tied to web mail providers,” the team wrote. “60 percent of the accounts were created with Hotmail, followed by and”

Bulk-created accounts at these Webmail providers are among the cheapest of the free email providers, probably because they lack additional account creation verification mechanisms required by competitors like Google, which relies on phone verification. Compare the prices at this bulk email merchant: 1,000 Yahoo accounts can be had for $10 (1 cent per account), and the same number Hotmail accounts go for $12. In contrast, it costs $200 to buy 1,000 Gmail accounts.

topcountriesFinally, the researchers discovered that Twitter account merchants very often spread their new account registrations across thousands of Internet addresses to avoid Twitter’s IP address blacklisting and throttling. They concluded that some of the larger account sellers have access to large botnets of hacked PCs that can be used as proxies during the registration process.

“Our analysis leads us to believe that account merchants either own or rent access to thousands of compromised hosts to evade IP defenses,” the researchers wrote.

Damon McCoy, an assistant professor of computer science at GMU and one of the authors of the study, said the top sources of the proxy IP addresses were computers in developing countries like India, Ukraine, Thailand, Mexico and Vietnam.  “These are countries where the price to buy installs [installations of malware that turns PCs into bots] is relatively low,” McCoy said.

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Jun 13

How Much is Your Gmail Worth?

If you use Gmail and have ever wondered how much your account might be worth to cyber thieves, have a look at Cloudsweeper, a new service launching this week that tries to price the value of your Gmail address based on the number of retail accounts you have tied to it and the current resale value of those accounts in the underground.

My Gmail was priced at $28.90.

My Gmail was priced at $28.90.

The brainchild of researchers at the University of Illinois at Chicago, Cloudsweeper’s account theft audit tool scans your inbox and presents a breakdown of how many accounts connected to that address an attacker could seize if he gained access to your Gmail. Cloudsweeper then tries to put an aggregate price tag on your inbox, a figure that’s computed by totaling the resale value of other account credentials that crooks can steal if they hijack your email.

In a blog post earlier this month titled The Value of a Hacked Email Account, I noted that many people do not realize how much they have invested in their email account until that account is in the hands of cyber crooks. That post quoted prices from one seller in the cybercrime underground who buys compromised accounts, such as hacked iTunes accounts for $8, or credentials to for $5, for example.

Chris Kanich, assistant professor at UIC’s computer science department and principal organizer of the project, said Cloudsweeper’s pricing model is built on prices collected from multiple sellers across multiple underground forums and services. I ran one of my Gmail accounts through Cloudsweeper, and it determined my account would be worth approximately $28.90 to bad guys. While this is not a Gmail account I use every day, I was surprised at how many third party services I had signed up for using it over the years. According to Cloudsweeper, bad guys with access to my account could also hijack my accounts at Amazon, Apple, Groupon, Hulu, NeweggPaypal, Skype, UPlay and Yahoo, to name a few.

Cloudsweeper uses the Open Authentication (OAuth2) protocol to connect to your Gmail account and search through messages. OAuth is an open standard for online authorization, and using it with Cloudsweeper does not require you to type in your password as long as you are already logged into the Gmail account that you’d like scanned. Cloudsweeper doesn’t keep your credentials, and it forgets about your visit and inbox after you log out of the service, or within 60 minutes of inactivity.


Prior to performing a scan, the service asks users if they wish to participate in a study, which Kanich said gathers and securely stores non-personally identifiable information about Cloudsweeper users who opt-in. That data includes how many types of accounts each user has tied to their Gmail. The study also draws on data from the second core feature of Cloudsweeper: The ability to discover and then redact or encrypt passwords that various services may send to users in plain text.

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Jan 13

Spam Volumes: Past & Present, Global & Local

Last week, National Public Radio aired a story on my Pharma Wars series, which chronicles an epic battle between men who ran two competing cybercrime empires that used spam to pimp online pharmacy sites. As I was working with the NPR reporter on the story, I was struck by how much spam has decreased over the past couple of years.

Below is a graphic that’s based on spam data collected by Symantec‘s MessageLabs. It shows that global spam volumes fell and spiked fairly regularly, from highs of 6 trillion messages sent per month to just below 1 trillion. I produced this graph based on Symantec’s raw spam data.


Some of the points on the graph where spam volumes fall precipitously roughly coincide with major disruptive events, such as the disconnection of rogue ISPs McColo Corp. and 3FN, as well as targeted takedowns against major spam botnets, including Bredolab, Rustock and Grum. Obviously, this graph shows a correlation to those events, not a direct causation; there may well have been other events other than those mentioned that caused decreases in junk email volumes worldwide. Nevertheless, it is clear that the closure of the SpamIt affiliate program in the fall of 2010 marked the beginning of a steep and steady decline of spam volumes that persists to this day.

Of course, spam volumes are relative, depending on where you live and which providers you rely on for email and connections to the larger Internet. As I was putting together these charts, I also asked for spam data from Cloudmark, a San Francisco-based email security firm. Their data (shown in the graphs below) paint a very interesting picture of the difference in percentage of email that is spam coming from users of the top three email services: The spam percentages were Yahoo! (22%), Microsoft (11%) and  Google (6%).


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Jul 12

Cyberheist Smokescreen: Email, Phone, SMS Floods

It was early October 2011, and I was on the treadmill checking email from my phone when I noticed several hundred new messages had arrived since I last looked at my Gmail inbox just 20 minutes earlier. I didn’t know it at the time, but my account was being used to beta test a private service now offered openly in the criminal underground that can be hired to create highly disruptive floods of junk email, text messages and phone calls.

Many businesses request some kind of confirmation from their bank whenever high-dollar transfers are initiated. These confirmations may be sent via text message or email, or the business may ask their bank to call them to verify requested transfers. The attack that hit my inbox was part of an offering that crooks can hire to flood each medium of communication, thereby preventing a targeted business from ever receiving or finding alerts from their bank.

Shortly after the email barrage began, I fired off a note to Google‘s public relations folks, asking for advice and assistance. Thankfully, my phone line was not a subject of the attack, and I was able to communicate what I was seeing to Google’s team. They worked to fight the attack for the better part of that day, during which time my inbox received tens of thousands of emails, burying hundreds of legitimate emails in page after page of junk messages (in the screen shot above, the note to Google spokesman Jay Nancarrow is at the top of the junk message pile).

What was most surprising about these messages was that many of them contained fairly spammy subject lines that should have been easily caught by Google’s junk mail filters. Each junk message contained nothing but pages full of garbled letters and numbers; the text of each missive resembled an encrypted message.

Google’s engineers managed to block a majority of the junk messages after about six hours, but the company declined to talk about what caused the attack to succeed. It took many more hours to sift through the junk messages to fish out the ones I wanted.

“This isn’t about a hole in Gmail or an exploit — it’s more a matter of spam dynamics and what may be able to get through more easily under certain circumstances,” Nancarrow said. “As a result, we can’t provide specifics that could aid spammers in trying new campaigns.”

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Jun 12

Attackers Hit Weak Spots in 2-Factor Authentication

An attack late last week that compromised the personal and business Gmail accounts of Matthew Prince, chief executive of Web content delivery system CloudFlare, revealed a subtle but dangerous security flaw in the 2-factor authentication process used in Google Apps for business customers. Google has since fixed the glitch, but the incident offers a timely reminder that two-factor authentication schemes are only as secure as their weakest component.

In a blog post on Friday, Prince wrote about a complicated attack in which miscreants were able to access a customer’s account on CloudFlare and change the customer’s DNS records. The attack succeeded, Prince said, in part because the perpetrators exploited a weakness in Google’s account recovery process to hijack his email address, which runs on Google Apps.

A Google spokesperson confirmed that the company “fixed a flaw that, under very specific conditions, existed in the account recovery process for Google Apps for Business customers.”

“If an administrator account that was configured to send password reset instructions to a registered secondary email address was successfully recovered, 2-step verification would have been disabled in the process,” the company said. “This could have led to abuse if their secondary email account was compromised through some other means. We resolved the issue last week to prevent further abuse.”

Prince acknowledged that the attackers also leveraged the fact that his recovery email address — his personal Gmail account — was not taking advantage of Google’s free 2-factor authentication offering. Prince claims that the final stage of the attack succeeded because the miscreants were able to trick his mobile phone provider — AT&T — into forwarding his voicemail to another account.

In a phone interview Monday, Prince said he received a phone call at 11:39 a.m. on Friday from a phone number in Chico, Calif. Not knowing anyone from that area, he let the call go to voicemail. Two minutes later, he received a voicemail that was a recorded message from Google saying that his personal Gmail account password had been changed. Prince said he then initiated the account recovery process himself and changed his password back, and that the hacker(s) and he continued to ping pong for control over the Gmail account, exchanging control 10 times in 15 minutes.

“The calls were being forwarded, because phone calls still came to me,” Prince said. “I didn’t realize my voicemail had been compromised until that evening when someone called me and soon after got a text message saying, ‘Hey, something is weird with your voicemail.'”

Gmail constantly nags users to tie a mobile phone number to their account, ostensibly so that those who forget their passwords or get locked out can have an automated, out-of-band way to receive a password reset code (Google also gets another way to link real-life identities connected to cell phone records with Gmail accounts that may not be so obviously tied to a specific identity). The default method of sending a reset code is via text message, but users can also select to receive the prompt via a phone call from Google.

The trouble is, Gmail users who haven’t availed themselves of Google’s 2-factor authentication offering (Google calls it “2-step verification”) are most likely at the mercy of the security of their mobile provider. For example, AT&T users who have not assigned a PIN to their voicemail accounts are vulnerable to outsiders listening to their voice messages, simply by spoofing the caller ID so that it matches the target’s own phone number. Prince said his AT&T PIN was a completely random 24-digit combination (and here I thought I was paranoid with a 12-digit PIN).

“Working with Google we believe we have discovered the vulnerability that allowed the hacker to access my personal Gmail account, which was what began the chain of events,” Prince wrote in an update to the blog post about the attack. “It appears to have involved a breach of AT&T’s systems that compromised the out-of-band verification. The upshot is that if an attacker knows your phone number and your phone number is listed as a possible recovery method for your Google account then, at best, your Google account may only be as secure as your voicemail PIN.”

AT&T officials did not respond to requests for comment.

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Sep 11

‘Right-to-Left Override’ Aids Email Attacks

Computer crooks and spammers are abusing a little-known encoding method that makes it easy to disguise malicious executable files (.exe) as relatively harmless documents, such as text or Microsoft Word files.

The “right to left override” (RLO) character is a special character within unicode, an encoding system that allows computers to exchange information regardless of the language used. Unicode covers all the characters for all writing systems of the world, modern and ancient. It also includes technical symbols, punctuations, and many other characters used in writing text. For example, a blank space between two letters, numbers or symbols is expressed in unicode as “U+0020”.

The RLO character (U+202e in unicode) is designed to support languages that are written right to left, such as Arabic and Hebrew. The problem is that this override character also can be used to make a malicious file look innocuous.

This threat is not new, and has been known for some time. But an increasing number of email based attacks are taking advantage of the RLO character to trick users who have been trained to be wary of clicking on random .exe files, according to Internet security firm Commtouch.

Take the following file, for example, which is encoded with the RLO character:


Looks like a Microsoft Word document, right? This was the lure used in a recent attack that downloaded Bredolab malware. The malicious file, CORP_INVOICE_08.14.2011_Pr.phyldoc.exe, was made to display as CORP_INVOICE_08.14.2011_Pr.phylexe.doc by placing the unicode command for right to left override just before the “d” in “doc”.

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Jul 11

How to Buy Friends and Deceive People

Want more friends and followers? Emerging enterprises will create them for you — for a price. An abundance of low-cost, freelance labor online is posing huge challenges for Internet companies trying to combat the growing abuse of their services, and has created a virtual testbed for emerging industries built to assist a range of cybercrime activities, new research shows.

Free services like Craigslist, Facebook, Gmail and Twitter have long sought to deter scammers and spammers by deploying technical countermeasures designed to prevent automated activity, such as the use of botnets to create new accounts en masse. These defenses typically require users to perform tasks that are difficult to automate, at least in theory, such as requiring that new accounts be verified by phone before activation.

But researchers from the University of California, San Diego found that these fraud controls increasingly are being defeated by freelance work arrangements: buyers “crowdsource” work by posting jobs they need done, and globally distributed workers bid on projects that they are willing to take on.

“The availability of this on-demand, for-hire contract market to do just about anything you can think of means it’s very easy for people to innovate around new scams,” said Stefan Savage, a UCSD computer science professor and co-author of the study.

The UCSD team examined almost seven years worth of data from, a popular marketplace for those looking for work. They found that 65-70 percent of the 84,000+ jobs offered for bidding during that time appeared to be for legitimate work such online content creation and Web programming. The remainder centered around four classes of what they termed “dirty” jobs, such as account registration and verification, social network linking (buying friends and followers), search engine optimization, and ad posting and bulk mailing.

“Though not widely appreciated, today there are vibrant markets for such abuse-oriented services,'” the researchers wrote. “In a matter of minutes, one can buy a thousand phone-verified Gmail accounts for $300, or a thousand Facebook ‘friends’ for $26 – all provided using extensive manual labor.”

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