Kelihos checks machines' IP addresses against DNS blacklists

Posted by   Virus Bulletin on   Aug 29, 2013

Role of node in a botnet dependent on whether the IP address is blacklisted.

Whenever I look at the results of the VBSpam tests, it always amazes me how large a percentage of spam is blocked because the sending IP address appears on a DNS blacklist.

It is not that I wouldn't expect those that maintain such blacklists not to do a good job: I know that they work hard to keep the lists up to date to block as much spam as possible. But I regularly wonder whether spammers care that most of the emails they send will be blocked by just about any blacklist in existence.

Some spammers apparently do care. In a post for the ZScaler blog, Chris Mannon analyses a recent Kelihos sample that I thought was interesting in this context.

Upon installation on a new machine, the malware queries the machine's public IP address against a number of widely used DNS blacklists. The role the node will play in the botnet then depends on whether or not the IP address is blacklisted: only if it isn't, will the machine be used to send spam.

The blacklisting of IP addresses isn't the only reason why botnet spam - especially when sent from compromised home PCs - is relatively easy to block. Sending spam only from addresses that don't appear on blacklists won't give the spammers a shortcut to users' inboxes - if only because it won't take long before these addresses end up being blacklisted too.

But it does show that cybercriminals haven't given up on spam - and are still actively trying to find ways to get their emails delivered. As can already be seen from some interesting posts on the Malware Must Die blog, despite a number of prominent 'shutdowns', Kelihos is still very much alive and kicking.

Posted on 29 August 2013 by Martijn Grooten



Latest posts:

VB2017 paper: The life story of an IPT - Inept Persistent Threat actor

At VB2017 in Madrid, Polish security researcher and journalist Adam Haertlé presented a paper about a very inept persistent threat. Today, we publish both the paper and the recording of Adam's presentation.

Five reasons to submit a VB2018 paper this weekend

The call for papers for VB2018 closes on 18 March, and while we've already received many great submissions, we still want more! Here are five reasons why you should submit a paper this weekend.

First partners of VB2018 announced

We are excited to announce the first six companies to partner with VB2018.

VB2018: looking for technical and non-technical talks

We like to pick good, solid technical talks for the VB conference programme, but good talks don't have to be technical and we welcome less technical submissions just as much.

Partner with VB2018 for extra visibility among industry peers

Partnering with the VB conference links your company to a successful and well-established event, demonstrates your commitment to moving the industry forward, allows you to meet potential clients, be visible to industry peers and build lasting…