Malware experts with Invicea report about a new type of fileless ransomware that has been sent to random users through a corrupted ad-bidding network in order to win an advertising spot on popular web pages. The threat is assumingly created by Russian cyber criminals.
The first step of the attack is the setup of a burner domain that redirects the victim to a landing page hosting the payload. Then the cyber crooks would engage in an actual real-time bidding for advertisements leading to the burner domain.
No Sign of a Malicious File on the Compromised Machine
As soon as the malicious ad is placed on a popular website, it’s a matter of time till users click on it and get redirected first to the malicious domain and then to the landing page.
The campaign lasts exactly eight hours, which is the time the DNS is set to be active on the burner domain. Then the cycle will repeat with another burner.
The malicious file the victim receives is not saved on the system’s storage unit. Experts say that it gets extracted directly in the system’s memory. In order to do so, it uses the “extract32.exe” tool in Windows.
The ransomware is said to come with protection against virtual environments. If it does not detect a protected space, the infection will start the file-encrypting process and display a ransom message demanding a certain fee in exchange for the private key needed for the decryption of the files on the compromised computer. The attack has been linked to numerous domains registered by a person with the following email address: “email@example.com”. This is why experts dubbed the attack Fessleak.
Fessleak Attack – Details
Experts report that as soon as the CVE-2015-0310, CVE-2015-0311 and CVE-2015-0313 zero-day exploits for Flash Player came out, the cyber criminals behind the attack have changed their strategy. Instead of the fileless approach, they chose to deliver the malware via typical Flash exploitation techniques.
The Invicea research team stated in a blog post that Fassleak now drops a temp file using Flash and “makes calls to icacls.exe”, which sets the permissions on files and folders. So far, the malicious binary cannot be detected. The experts believe that it rotates its hash value in order to avoid detection by antivirus software.
So far, the following websites have been reported to display corrupted ads:
The malware experts with Invicea have been following the attackers for quite some time now. Reportedly, the Fessleak has been active since October 17, 2014. The most recent attack has been the one on Thebrofessional.net on February 3, 2015.
Remove Fessleak and Restore the Encrypted Files
Stage One: Remove Fessleak
1. First and most important – download and install a legitimate and trustworthy anti-malware scanner, which will help you run a full system scan and eliminate all threats.
Spy Hunter FREE scanner will only detect the threat. If you want the threat to be automatically removed, you need to purchase the full version of the malware tool. Find Out More About SpyHunter Anti-Malware Tool
2. Run a second scan to make sure that there are no malicious software programs running on your PC. For that purpose, it’s recommended to download ESET Online Scanner.
Your PC should be clean now.
Stage Two: Restore the Encrypted Files
Option 1: Best case scenario – You have backed up your data on a regular basis, and now you can use the most recent backup to restore your files.
Option 2: Try to decrypt your files with the help of Kaspersky’s RectorDecryptor.exe and RakhniDecryptor.exe. They might help you in the process but keep in mind that they were not specially designed to encrypt information that was decrypted by this particular ransomware.
Option 3: Shadow Volume Copies
1. Install the Shadow Explorer, which is available with Windows Vista, Windows 7, Windows 8 and Windows XP Service Pack 2.
2. From Shadow Explorer’s drop down menu choose a drive and the latest date you would like to restore information from.
3. Right-click on a random encrypted file or folder then select “Export”. Select a location to restore the content of the selected file or folder.
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It is highly recommended to run a FREE scan before purchasing the full version of the software to make sure that the current version of the malware can be detected by SpyHunter.