Attackers conceal exploit sites with Twitter API

Trends technique suffers hacktile dysfunction

Drive-by exploit writers have been spotted using a popular Twitter command to send web surfers to malicious sites, a technique that helps conceal the devious deed.

The microblogging site makes application programming interfaces (APIs) such as this one available so legitimate websites can easily plug into the top topics being tweeted. As the concerns and opinions of Twitter users change over time, so too will the so-called top 30 trending topics.

But it turns out that the API for generating the never-ending stream of keywords is being used by miscreants, too. According to researcher Denis Sinegubko, it's being added to heavily obfuscated redirection scripts injected into compromised websites. The scripts, which redirect victims to drive-by sites that attempt to exploit unpatched vulnerabilities in programs such as Apple's QuickTime, use the second letter of a trending topic to arrive at a secret code that's a key ingredient in determining the contents of the domain.

The top term "Jedward" from a few days ago, for instance, becomes ghoizwvlev.com. Other domain names generated this month included abirgqvlev.com, fgxhzgvlev.com and abxhcgvlev.com.

"To make the domain name generation less predictable, they use the code of the second character in the Twitter search that was the most popular two days earlier," Sinegubko writes. "This way they have one day to register a new domain name that will be active the next day."

The Twitter API is a useful weapon in the miscreant's arsenal because it helps prevent malicious scripts from being caught by scanners searching for malicious domain names in web scripts. Instead of seeing a URL known to be distributing malware, the scanners see a widely used API for one of the world's most popular websites.

If the scheme sounds like a lot of work to keep drive-by exploit sites concealed, you're right. Something seems to have gone wrong, and of the many generated names Sinegubko checked, only one was registered, and that one suffered from internal errors.

Still, the technique shows the continuing evolution of attackers striving to find new ways to cloak drive-by attacks. And based on this analysis of the Torpig botnet, Sinegubko isn't the only white hat hacker who has stumbled onto it.

"This is probably the most creative malicious script I've seen so far," Sinegubko writes. "Luckily for us, it was not very well thought out."