A Patched remote code execution Microsoft Office Vulnerability ( CVE-2017-11882) abusing again and using it for spreading a variety of Malware such as FAREIT, Ursnif and a Keylogger Loki info stealer that is used for stealing Crypto wallet password.
In this case, some of the uncommon methods has been reused by helping of Windows Installer service Windows.
Previous Exploitation did using the Windows executable mshta.exe to run a Powershell script. but this attack using uses msiexec.exe Exploit this Vulnerability.
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Various other methods such as Wscript, Powershell, Mshta.exe, Winword.exe is very common methods and security software are easily monitoring these methods if other malware is abusing these function.
But use of msiexec.exe to download malware is not something regular way to abuse the victims.
How Does this Office Vulnerability has Abused
The initial level of infection spreading via spam email Campaign that contains a malicious attachment file that claimed as a payment copy with order confirmation body content.
Body content is Written in Korean language and given fake warning as,” please check if your PC may be infected by a virus or malicious codes”.
An attacked Document file which claimed as payment copy is an actual exploit of CVE-2017-11882.
Later it uses the command that will instruct to Exploit this vulnerability and it leads to download and install the malicious MSI package labeled zus.msi through Windows Installer.
According to Trend Micro, Later MSIL or Delphi binary will be installed by Windows Installer (msiexec.exe) and some time based on the MSI package it may contain either a heavily obfuscated Microsoft Intermediate Language (MSIL) or Delphi binary file, which then acts as a loader for the actual payload.
Moreover, it using obfuscation to evade the antivirus scanners and being detected by an anti-malware scanner is more difficult since its using heavily obfuscated MSIL or Delphi binary.
In this analyse it usually download and install the LokiBot Keylogger variant but it capable to download and execute other malware as well.
Mitigation
— Always keep your OS and software updated
— Train staff never open attachments or click on a URL in unsolicited e-mails
— Use Anti Spam Gateway such as Comodo Anti spam Gateway for defense against spam, phishing emails, and virus-infected attachments
— Turn on Your Firewall
— Limit the user Privilege
— Use caution when clicking on links to web pages
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