Twitter Being Used As Botnet Command Channel

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Ah Twitter in the news again, the bad guys sure do keep up with new trends. After being taken offline for a while by a Joejob DDoS attack Twitter is in the news again – this time it’s being used as the command channel for a Botnet.

The normal method for controlling Botnets is via an IRC channel, usually a private keyed channel on some obscure network. A lot of people used to use EFnet due to it’s lack of network services, but nowdays there are so many networks to choose from people can keep out of the limelight.

Sometimes even using a private IRCd setup on a hacked server or via Dynamic DNS on a home server.

For the past couple weeks, Twitter has come under attacks that besieged it with more traffic than it could handle. Now comes evidence that the microblogging website is being used to feed the very types of infected machines that took it out of commission.

That’s the conclusion of Jose Nazario, the manager of security research at Arbor Networks. On Thursday, he stumbled upon a Twitter account that was being used as part of an improvised update server for computers that are part of a botnet.

The account, which Twitter promptly suspended, issued tweets containing a single line of text that looked indecipherable to the naked eye. Using what’s known as a base64 decoder, however, the dispatches pointed to links where infected computers could receive malware updates.

Ok so one such channel was discovered, how many more accounts are there on Twitter being used for nefarious purposes?

Very hard for anyone to track them down, especially if they don’t use standard syntax across all the accounts.

I’m sure Twitter will be thinking up some way to auto-discover these accounts.

Master command channels used to herd large numbers of infected machines have long been one of the weak links in the botnet trade. Not only do they cost money to maintain, but they can provide tell-tale clues that help law enforcement agents to track down the miscreants running the rogue networks. Bot herders have used ICQ, internet relay chat, and other chat mediums to get around this limitation, but this appears to be the first time Twitter is known to have been employed.

Nazario said he’s found at least two other Twitter accounts he suspects were being used in the same fashion, but needs to do additional analysis before he can be sure. The bots using the Twitter account connected using RSS feeds, a technique that allowed them to receive each tweet in real time without the need of an account. It was unclear how many bots connected to the account.

Up to now, the bot designers have done a good job keeping their enterprise under wraps. The original bot software is detected by just 46 percent of the major anti-virus tools, according to this VirusTotal analysis. The updates, which appear to be affiliated with the Buzus trojan, are even stealthier, with only 22 percent of AV engines detecting it.

The example discovered uses base64 encoding, so perhaps they can track down accounts with base64 strings in their feed.

You can read more on the Arbor Networks blog here:

Twitter-based Botnet Command Channel

Source: The Register