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6 January 2020

Fileless click-fraud malware



It’s holiday today. Lots of kids will be opening presents and playing with new toys. However, I’m here as every week. I’m reading and writing about malware. I read the the evolution of the fileless click-fraud malware Poweliks last week and I wanted to read it deeply and write about it. I think this is the best way to learn and get knowledge about this kind of malware. I’ve already written about fileless malware forensics. Therefore, I know a little bit how these malware work. Today, I’m going to deep down in tricks and innovations of the fileless click-fraud malware Poweliks.

The first innovation is the registry protection. It’s a trick used by this fileless malware which inserts an extra registry subkey. This subkey contains an entry with the 0x06 byte and the 0x08 byte, which are not Unicode printable character sets, thus it is difficult to read and delete properly. For instance, we won’t be able to read and delete this subkey with the default Windows Registry Editor. Therefore, we’ll need another registry tool to handle these special characters. In addition, administrative users won’t be able to delete this subkey thus permissions must be modified in order to delete the unreadable entry.

Extra registry subkey to protect Poweliks in memory

Another innovation is the CLSID hijacking. A CLSID or Class Identifier is a globally unique identifier that is used to represent a specific instance of a program. It allows operating systems and software to detect and access software components without identifying them by their names. CLSID hijacking is used by fileless malware to implant DLLs. These DLLs will be launched legitimately by trusted and whitelisted processes such as explorer.exe, chrome, iexplorer, etc.

The third trick or innovation is the fileless persistence. Lots of malware hide a malicious executable on the compromised computer which is then executed. However, fileless malware don’t store anything on disk. They save malicious code in the Windows Registry which is executed to load malicious DLLs. For instance, the fileless malware Poweliks executes rundll32.exe with several parameters, one of them is a JavaScript code used to load the malware into the memory.

Loading JavaScript code through the registry
 
Most fileless malware need an exploit to insert the code into the Windows Registry. For instance, Poweliks was using a Windows zero-day exploit for privilege escalation. Thanks to this zero-day vulnerability, Poweliks run regedit to insert the malicious code into the Windows Registry. In addition, Poweliks was using this vulnerability to run a batch file.

Finally, how these malware put the money in the pocket? A fileless click-fraud malware is going to click lots of ads. However, the victim doesn’t know the computer is clicking too many ads. Meanwhile, attackers generates money to be paid by the advertiser to the publisher. In addition, this kind of malware can also download more malware. For instance, one of the websites visited by Poweliks resulted in Cryptowall being installed on the computer.

Poweliks advertisement request
 
To sum up. It’s holiday. There are lots of gifts and presents today. I wish you many and lots this year. However, open the eyes! Be caution! Protect your systems!!

Have a nice day!

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