Posts Tagged: Matthew Prince

Feb 14

The New Normal: 200-400 Gbps DDoS Attacks

Over the past four years, KrebsOnSecurity has been targeted by countless denial-of-service attacks intended to knock it offline. Earlier this week, KrebsOnSecurity was hit by easily the most massive and intense such attack yet — a nearly 200 Gbps assault leveraging a simple attack method that industry experts say is becoming alarmingly common.


At issue is a seemingly harmless feature built into many Internet servers known as the Network Time Protocol (NTP), which is used to sync the date and time between machines on a network. The problem isn’t with NTP itself, per se, but with certain outdated or hard-coded implementations of it that attackers can use to turn a relatively negligible attack into something much, much bigger. Symantec‘s writeup on this threat from December 2013 explains the problem succinctly:

Similar to DNS amplification attacks, the attacker sends a small forged packet that requests a large amount of data be sent to the target IP Address. In this case, the attackers are taking advantage of the monlist command.  Monlist is a remote command in older version of NTP that sends the requester a list of the last 600 hosts who have connected to that server.  For attackers the monlist query is a great reconnaissance tool.  For a localized NTP server it can help to build a network profile.  However, as a DDoS tool, it is even better because a small query can redirect megabytes worth of traffic.

Matthew Prince, the CEO of Cloudflare — a company that helps Web sites stay online in the face of huge DDoS attacks — blogged Thursday about a nearly 400 Gbps attack that recently hit one of the company’s customers and leveraged NTP amplification. Prince said that while Cloudflare “generally [was] able to mitigate the attack, it was large enough that it caused network congestion in parts of Europe.”

“Monday’s DDoS proved these attacks aren’t just theoretical. To generate approximately 400Gbps of traffic, the attacker used 4,529 NTP servers running on 1,298 different networks,” Prince wrote. “On average, each of these servers sent 87Mbps of traffic to the intended victim on CloudFlare’s network. Remarkably, it is possible that the attacker used only a single server running on a network that allowed source IP address spoofing to initiate the requests. An attacker with a 1 Gbps connection can theoretically generate more than 200Gbps of DDoS traffic.” Continue reading →

Apr 13

Brute Force Attacks Build WordPress Botnet

Security experts are warning that an escalating series of online attacks designed to break into poorly-secured WordPress blogs is fueling the growth of an unusually powerful botnet currently made up of more than 90,000 Web servers.



Over the past week, analysts from a variety of security and networking firms have tracked an alarming uptick in so-called “brute force” password-guessing attacks against Web sites powered by WordPress, perhaps the most popular content management system in use today (this blog also runs WordPress).

According to Web site security firm Incapsula, those responsible for this crime campaign are scanning the Internet for WordPress installations, and then attempting to log in to the administrative console at these sites using a custom list of approximately 1,000 of the most commonly-used username and password combinations.

Incapsula co-founder Marc Gaffan told KrebsOnSecurity that infected sites will be seeded with a backdoor the lets the attackers control the site remotely (the backdoors persist regardless of whether the legitimate site owner subsequently changes his password). The infected sites then are conscripted into the attacking server botnet, and forced to launch password-guessing attacks against other sites running WordPress.

Gaffan said the traffic being generated by all this activity is wreaking havoc for some Web hosting firms.

“It’s hurting the service providers the most, not just with incoming traffic,” Gaffan said. “But as soon as those servers get hacked, they are now bombarding other servers with attack traffic. We’re talking about Web servers, not home PCs. PCs maybe connected to the Internet with a 10 megabit or 20 megabit line, but the best hosting providers have essentially unlimited Internet bandwidth. We think they’re building an army of zombies, big servers to bombard other targets for a bigger cause down the road.”

Indeed, this was the message driven home Thursday in a blog post from Houston, Texas based HostGator, one of the largest hosting providers in the United States. The company’s data suggests that the botnet of infected WordPress installations now includes more than 90,000 compromised sites.

Continue reading →

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.

Continue reading →