Botnets Serving Up More Multipurpose Malware

In a troubling trend for enterprises, an analysis of botnet activity in the first six months of 2018 shows that multifunctional malware tools are becoming increasingly popular among attackers.

Kaspersky Lab inspected more than 150 malware families and their modifications across some 60,000 botnets around the world and found that the share of multipurpose Remote Access Tools has almost doubled on botnets since the beginning of 2017 - from 6.5% to 12.2%.

The three most widespread of these RATs or backdoors—Njrat, DarkComet, and Nanocore—are all malware tools that attackers can relatively easily modify for different purposes or adapt for distribution in specific regions. Kaspersky Lab discovered Njrat to have command and control centers in 99 countries, mainly because of how easily attackers can use it to configure a personal backdoor with very little knowledge of malware development. Nanocore and DarkComet have C2 centers in over 80 countries for the same reason.

Similarly, Trojans capable of being modified and controlled by different command and control servers and used for different purposes were another category of malware that grew in Q1, though not quite as dramatically as RATs. Kaspersky Lab's analysis showed that the share of such Trojans increased from 32.9% in the second half of 2017 to around 34.3% in the first six months of 2018.

Over the same period, the proportion of single-purpose tools being distributed through botnets declined substantially. For example, the share of special-purpose banking Trojans distributed via botnets dropped over 9.2%, from around 22.5% in the second half of 2017 to 13.3% of all malicious files in the first half of 2018.

Similarly, the share of spamming bots, which are another category of single-purpose malware, dropped to 12.2% this year from almost 19% in H2 of 2017. DDoS bots—another category of single-purpose tool—followed a similar pattern dropping from around 3% in Q3 and Q4 last year to about 2.7% in the first six months of this year.

Botnets on a Budget

One factor driving the trend is the relatively high costs of operating a botnet, says Alexander Eremin, security expert at Kaspersky Lab. Bots can be costly, so botmasters are looking for every opportunity to make money from their malware tools. Multi-purpose malware allows bot owners to quickly adapt their network for different purposes: from delivering spam, for instance, to distributing banking Trojans and ransomware, he says.

"[The] trend is driven by significant botnet ownership costs. Criminals will attempt to take everything at the first chance," Eremin notes. "The emergence of multifunctional malware means that users need powerful protection as criminals try to steal users’ credentials, money, sensitive data, using the same malware sample."

Botnets increasingly are being used according to the needs of the operator at that time, so it is often difficult to identify the primary specialization of a botnet, he says.

The Kaspersky Lab report is the second in recent weeks to warn about an increase in multi-purpose and adaptive malware tools. Earlier this month security vendor Proofpoint said it had seen a recent increase in the use of modular downloaders that allow attackers to modify malware after it has been installed on a system.

Basically, the tools allow adversaries to fingerprint infected systems and then modify or update the malware based on items of interest that the downloader might identify on a system.

Modular malware like the multiple-purpose tools that Kaspersky Lab highlighted in its report this week is problematic for enterprises because of how it can be quickly adapted for a variety of different tasks.

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