Over the Kazuar’s nest: Cracking down on a freshly hatched backdoor used by Pensive Ursa

While tracking the evolution of Pensive Ursa (aka Turla, Uroburos), Unit 42 researchers came across a new, upgraded variant of Kazuar. Not only is Kazuar another name for the enormous and dangerous cassowary bird, Kazuar is an advanced and stealthy .NET backdoor that Pensive Ursa usually uses as a second stage payload.

Pensive Ursa is a Russian-based threat group operating since at least 2004, which is linked to the Russian Federal Security Service (FSB). The Ukrainian CERT reported in July 2023 that this version of Kazuar was targeting the Ukrainian defense sector. The threat group behind this variant was going after sensitive assets such as those found in Signal messages, source control and cloud platforms data.

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Source: Palo Alto Unit 42