In the last days, a huge attack campaign hit several organizations across the Italian cyberspace, as stated on bulletin N020219 the attack waves tried to impersonate legit communication from a known Express Courier. However, a deeper analysis by
|Desc||Obfuscated malicious JS. This download first component and keep communication with C2 server.|
Table 1: Generic information about malicious js file
This JS file is an obfuscated dropper with the purpose to download another component from a “safe” remote location:
As shown in Figure 3, the first characters of the encoded payload string are “TVNDRg” which translates to “MSCF”: standard header of the Microsoft Cabinet compressed file format.
Actually, this .CAB archive is just a shell for a PE32 executable file:
|Desc||First component downloaded by malicious js file.|
Table 2: Generic information about RuntimeBroker5.exe (AZORult)
Executing the RuntimeBroker5.exe sample, seems it behaves as another dropper: it downloads two other components from the remote server “hairpd[.]com”.
The sample file actually does not perform only this downlaod. Here one of the key point of the article: it also establishes a communication channel with the AZORult C2 host “ssl.]admin.]itybuy.]it”.
The network packet exchanged with the server confirms this identification due to the known communication patterns and the dynamic analysis also shows info-stealing behaviours compatible with the identified threat.
As shown in the following figure, the written files in “%APPDATA%\Local\Temp\” path closely match AZORult analysis described by Unit42 research group.
During the dynamic analysis, the RuntimeBroker5.exe sample received a sort of configuration file from the C2 server. We extracted it from the running malware image and decoded it:
Table 3: AZORult Configuration file
The multiple references to Browser Cookies and CryptoWallets confirms the “RuntimeBroker5.exe” sample, initially hidden into the cabilet archive, is an AZORult variant.
The other file download from hairpd[.]com by AZORult’s sample is another executable PE32.
|Descrizione Breve||Second component downloaded by malware. This component is alive after the infection.|
Table 4: Generic information about sputik.exe (Gootkit)
The “sputik.exe” uses a set of evasion techniques to avoid the monitoring of the process, such as invoking the “UuidCreateSequential” API to detect the usage of typical virtual machine’s MAC addresses, but this technique can be easily bypassed by spoofing a real network card one.
Bypassing all the evasion techniques reveals the nature of the payload: a Gootkit malware implant.
In the past years, Gootkit source code have been leaked online and part of it is also available on the Github platform. This way we were able to investigate differences between the extracted snippets and the known, previously leaked, malware version.
As general consideration, we noticed a lot of similarities between the codes, they are perfectly compatible, but few differences holds. For instance private keys and certificates have been modified, showing the malware author choose a stronger key.
Table 5: Certificate comparison
(New on the left, known/leaked on the right)
These attack waves targeting italian organization and users revealed interesting connections between two threats we was used to monitor and detect across both the InfoSec community and the CERT-Yoroi’s constituency, revealing a hidden link connecting this particular AZORult instance and with the Gootkit implant.
Also, the analysis pointed to an evolution of the dropping techniques used in the initial stages of the attacks by cyber-criminals, showing how the usage of extremely flexible stagers written in
Further details, including Indicators of Compromise (IoCs), are reported in the analysis published on the Yoroi Blog.
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(SecurityAffairs – AZORult, gootkit)
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