Hackers Using BlueShell Malware to Attack Windows, Linux, and Mac Systems

The usage of Blueshell malware spikes up by various threat actors to target Windows, Linux, and other operating systems across Korea and Thailand.

Blueshell backdoor malware has been active since 2020 and written in GO language, believed to be created by a Chinese user, which is available on the GitHub repository.

Though the original GitHub repository was deleted, BlueShell’s source code can still be accessed from other repositories. 

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AhnLab Security Emergency Response Center (ASEC) monitors APT attack cases using BlueShell and has released the summarized report of APT attack cases using BlueShell.

Considering the functionality of the Backshell, it is designed and uses TLS encryption to circumvent network detection with the C&C server. 

The Remote command execution, file download/upload, and Socks5 proxy were executed by the attacker through commands.

BlueShell has three configuration data: the C&C server’s IP address, port number, and waiting time. 

The research revealed the usage of blue shell malware by Dalbit Group during the attack against the Windows platform.

The Dalbit Group is a China-based threat group that mostly targets vulnerable servers to steal information containing critical data to demand money.

“While ASEC was monitoring BlueShell targeting the Linux environment, it identified a customized form of BlueShell from VirusTotal.”

The attacker first created Dropper malware and used it to install BlueShell, which is responsible for creating and executing BlueShell like a regular dropper.

But the main difference is that it sets and executes an environment variable named “lgdt” when running. 

The generated BlueShell obtains the “lgdt” environment variable, decrypts it, and uses it as the C&C server address. Accordingly, BlueShell alone cannot verify the address of the C&C server.

Indicator of compromise

– 53271b2ab6c327a68e78a7c0bf9f4044 
– 011cedd9932207ee5539895e2a1ed60a 
–7d9c233b8c9e3f0ea290d2b84593c842  
– 31c4a3f16baa5e0437fdd4603987b812
– 9f55b31c66a01953c17eea6ace66f636
– 33129e959221bf9d5211710747fddabe
-e0f4afe374d75608d604fbf108eac64f
– 96ec8798bba011d5be952e0e6398795d 
– b434df66d0dd15c2f5e5b2975f2cfbe2 
– f4ace89337c8448f13d6eb538a79ce30 
– 5e0845a9f08c1cfc7966824758b6953a
– e981219f6ba673e977c5c1771f86b189

– 85a6e4448f4e5be1aa135861a2c35d35
-21c7b2e6e0fb603c5fdd33781ac84b8f 
– 1a0c704611395b53f632d4f6119ed20c
– 4eb724cc5f3d94510ba5fc8d4dba6bb6
– 47fc0ecb87c1296b860b2e10d119fc6c 
– 2ed0a868520c31e27e69a0ab1a4e6 90d
-985000d076e7720660ab8435639d5ad5
-425c761a125b7cb674887121312bd16c
– 3f022d65129238c2d34e41deba3e24d3 
– 30fe6a0ba1d77e05a19d87fcf99e7ca5

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