Malware Information

Distribution of Word File (External + RTF) Modified to Avoid Detection

Malicious MS Office Word documents have long been used for the distribution of additional RTF malware by exploiting the fact that Word files allow external connection. However, AhnLab has identified the files that seem to have been made to avoid anti-malware detection are being distributed in Korea. Similar to past cases, an email disguised as a work email with a Word document attachment is used, but a unique factor exists in the webSettings.xml.rels file which can be identified within the…

Penetration and Distribution Method of Gwisin Attacker

The attacker of Gwisin ransomware targets and penetrates the publicly available servers of companies. They then use the server as their foothold for distributing the ransomware into the internal infrastructure. It is known that the attacker uses various means such as SFTP, WMI, integrated management solution, and IIS web service to distribute the ransomware into the internal infrastructure. In this confirmed case, they used the IIS web service to distribute Gwisin ransomware.  How Gwisin Attacker Penetrates a Server Unlike other…

LockBit 3.0 Being Distributed via Amadey Bot

The ASEC analysis team has confirmed that attackers are using Amadey Bot to install LockBit. Amadey Bot, a malware that was first discovered in 2018, is capable of stealing information and installing additional malware by receiving commands from the attacker. Like other malware strains, it is being sold in illegal forums and still being used by various attackers. It was used in the past to install ransomware by attackers of GandCrab or to install FlawedAmmyy by the TA505 group which…

Surtr Ransomware Being Distributed in Korea

Through internal monitoring, the ASEC analysis team has recently discovered that Surtr ransomware is being distributed. This ransomware encrypts files, then adds a “[DycripterSupp@mailfence.com].[<random string>].Surtr” file extension to the original file extension name. When Surtr ransomware infects a system, it changes the desktop image of the infected PC and creates a ransom note (See Figures 1 and 2) to inform the user of the ransomware infection. Surtr also creates ransom note files (SURTR_README.hta and SURTR_README.txt) in folders containing the infected…

Appleseed Being Distributed to Nuclear Power Plant-Related Companies

The ASEC analysis team has recently discovered a case of AppleSeed being distributed to nuclear power plant-related companies. AppleSeed is a backdoor malware used by Kimsuky, one of the organizations affiliated with North Korea, and this malware is being actively distributed to many companies. The filenames of the AppleSeed dropper were identified by the ASEC analysis team as follows, and a double file extension was used to deceive users. When the file is executed, the encoded data inside is decoded…