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Kelihos is a new spin on an old threat

Uses legitimate sources to gather intelligence

Chris Mannon, security researcher at Zscaler ThreatLabZ is warning that the Kelihos botnet is using some natty technology which puts new spin on an old threat.

Kelihos is a botnet which utilises P2P communication to maintain its command and control network and it apparently be picked up 30/45 AV vendors. Mannon had a look at the installer and found a file called "rasta01.exe". The file uses P2P style communication via SMTP. This particular instance called out to 159 distinct IP addresses. The botnet overtly installs several packet capturing utilities and services. This is done so that the infection can monitor ports 21, 25, and 110 for username and password information.

The botnet attempts to categorise it's new victim by using legitimate services to gather intelligence. In this instance, the malicious file actually queried the victim IP address on Barracuda Networks, SpamHaus, Mail-Abuse, and Sophos.

These services primarily exist to notify users of abuse seen on the site or IP address. Kelihos is using it to to determine if the new victim is already seen as malicious or not. If the victim isn't seen in the Composite Block Lists yet, then it may be used as either a Proxy C&C or Spam-bot.

The botnet makes no attempt to hide exactly how loud it is regarding network activity. We noted a spike in TCP traffic across a distinct 563 IP addresses in the span of two minutes. He warned network administrators should take extra care in monitoring users with anomalous levels of traffic. A single node giving off so much traffic to different services in such a small window could be used to identify potential victims, Mannon wrote.

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