5ss5c Ransomware
The threat actors behind the Satan, DBGer and Lucky ransomware, are back with a new piece of malware named ‘5ss5c’. Like Satan, 5ss5c launches process via a downloader and leverages the EternalBlue exploit for spreading. The downloader for the 5ss5c ransomware fetches and leverages the following:
- EternalBlue exploit and hardcoded credentials
- Mimikatz and another password stealer or dumper
- The actual ransomware 5ss5c as a second-stage malware
The dropper provides hardcoded credentials for the command-and-control (C2) server for the ransomware to connect to an SQL database. 5ss5c has an entirely fresh list of files to be encrypted. It only encrypt files with extensions 7z, bak, cer, csv, db, dbf, dmp, docx, eps, ldf, mdb, mdf, myd, myi, ora, pdf, pem, pfx, ppt, pptx, psd, rar, rtf, sql, tar, txt, vdi, vmdk, vmx, xls, xlsx and zip. As evident, this list primarily includes documents, archives, database files and VMware-related extensions like vmdk. The 5ss5c ransomware drops a ransom note in Chinese that demands a ransom of 1 bitcoin for decryption. The ransom note doesn’t include attackers’email to contact for the payment or a Bitcoin address, instead, the ransomware prepends the email address (5ss5c(at)mail[.]ru) to the file name of each encrypted file.
Countermeasures
- The majority of the ransomware infections are primarily introduced via phishing emails, malicious adverts on websites, and third-party apps and programs. Hence, thoughtfully designed security awareness campaigns that stress the avoidance of clicking on links and attachments in email, can establish an essential pillar of ransomware defense.
- It is crucial to install an active instance of a reputed multi-layered anti-malware solution updated with the latest signatures in all endpoint devices which will help reduce the gravity of such attacks.
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Monitor Connection attempts towards the listed domains /IPs. The list may include compromised domains /IP resources as well. Blocking the domains/IPs is solely the recipient's responsibility after diligently verifying them without impacting the operations.
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The key infection vector of 5ss5c involves exploiting vulnerabilities, especially the EternalBlue exploit; thus patching the specifically targeted vulnerabilities will reduce the attack window for the ransomware.
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Ransomware infections like 5ss5c primarily keep data as a hostage. Therefore, practicing regular backup of critical data can save the business in the event of such outbreaks. Also please ensure to maintain offline backups.
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All operating systems and applications should be kept updated on a regular basis. Virtual patching can be considered for protecting legacy systems and networks. This measure hinders cybercriminals from gaining easy access to any system through vulnerabilities in outdated applications and software. Avoid applying updates/patches available in any unofficial channel.
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Segmenting the critical networks and vulnerable or hard to secure systems from the rest of the network intelligently could serve as an effective shield against such attacks.