APT reports

Myrtus and Guava, Episode 4

A few days ago we wrote about a new variant of the Stuxnet worm’s rootkit component, signed not with Realtek’s digital signature, but with one owned by JMicron. Costin posted about it in detail.

The media jumped on the news, and there was a lot of talk about “New worm variant discovered”. However, the situation isn’t quite as simple as the headlines made out.

There wasn’t a clear answer to the main question i.e. where’s the worm which the signed driver would have come from? The fact that the driver was created on 14 July could indicate that a new variant of the worm, potentially with new functionality, was out in the wild.

However, all of our attempts to find the dropper of the second rootkit driver (there are meant to be two) came to nothing.

Over the last few days, all the discussions have boiled down to two possible explanations: either cybercriminals stole the digital certificates using a Trojan, or it was the work of an insider. Our failure to find the dropper or second driver, though, makes the whole story all the more complicated.

So we decided to look at some statistics: how many times has the Kaspersky Security Network detected Rootkit.Win32.Stuxnet.c (the driver signed with the JMicron certificate)? The numbers are discouraging – since 20 July, the module’s been detected all of twice, once in Russia and once in Ukraine. These figures look pretty silly when compared to the detection statistics for the rootkit component signed with the Realtek signature.

Verisign has now revoked the JMicron certificate, making it invalid. Our allowlisting database contained 124 programs which had been signed using the certificate – all of them, of course, were clean.

At the moment, I’m not drawing any conclusions about the origins of this mythical driver. I don’t doubt that it is a modified variant of mrxcls.sys. We’re still looking for whatever is launching it, or computers which it’s infected.

If we look at the stats relating to the initial Stuxnet variant, they show epidemics in India, Iran, and Indonesia. The number of infected computers increases by about a thousand every day, and this is only what our monitoring systems show us. In other words, it’s merely the tip of the iceberg.

Apart from the three countries hit by Stuxnet, Azerbaijan and Afghanistan have also been heavily affected, with more than a thousand infected machines each.

The geographical spread of the Trojan, together with the “missing” variant, has given us all a lot to think about.

Myrtus and Guava, Episode 4

Your email address will not be published. Required fields are marked *



The leap of a Cycldek-related threat actor

The investigation described in this article started with one such file which caught our attention due to the various improvements it brought to this well-known infection vector.

Lazarus targets defense industry with ThreatNeedle

In mid-2020, we realized that Lazarus was launching attacks on the defense industry using the ThreatNeedle cluster, an advanced malware cluster of Manuscrypt (a.k.a. NukeSped). While investigating this activity, we were able to observe the complete life cycle of an attack, uncovering more technical details and links to the group’s other campaigns.

Sunburst backdoor – code overlaps with Kazuar

While looking at the Sunburst backdoor, we discovered several features that overlap with a previously identified backdoor known as Kazuar. Our observations shows that Kazuar was used together with Turla tools during multiple breaches in past years.

Subscribe to our weekly e-mails

The hottest research right in your inbox