Rewterz Threat Alert – RATs Wrapped and Hidden in PNG

Severity

High

Analysis Summary

A recent campaign is pushing 2 RATs, encrypted, packed, and hidden in PNG files – using disk image files again and redirectors as arrival vectors.

The first spam campaign is about fake harassment. The sender, claiming to be a school president, is informing his colleague that an anonymous email with video, supposedly in the attachment, shows sexual harassment occurred on their premises.

The attachment CONFIDENTIAL0056.zip is a ZIP archive. Inside it is a disk image file CONFIDENTIAL0056.iso which is the Universal Disk Format (UDF) file system format. The image file CONFIDENTIAL0056.iso contains a RAR self-extracting archive (RARSfx) file PRIORITY.scr. Once launched, the RARSfx will silently drop and install 3 files in the %temp% folder. First, a shortcut file Xnekm.lnk will be created. It points to and therefore runs an executable Zhknjdc.exe which is in a folder with the same name as the LNK file. Stored with the EXE file is an image file Zhkn.png. 

A related spam campaign was spotted using fake purchase emails. The attachment PO-1109017834665.xlsx.html, disguised as an order slip, is an HTML redirector. It contains a META refresh tag that leads to the download of a RAR file. The HTML also has a hidden paragraph tag with random word padding causing the huge file size of the attachment.

The downloaded file PO-1109017834665.xlsx.rar is a RAR archive which contains 1 file PO-1109017834665.xlsx.exe – a Delphi compiled executable. The EXE’s behavior is almost the same with the EXE file dropped by RARSfx from the first campaign, except the associated PNG is located at its overlay, in other words appended to the end of the executable.

Impact

• Unauthorized Remote Access
• Code Execution
• Theft of information 

Indicators of Compromise

Domain Name

• rneiko-elec[.]com
• checker[.]rneiko-elec[.]com

Filename

• CONFIDENTIAL0056[.]iso
• PRIORITY[.]scr[.]rar
• Xnekm[.]lnk
• Zhknjdc[.]exe
• Zhkn[.]png
• Zhknasx[.]exe
• Zhkn_eno[.]hta
• Zhknwen[.]vbs
• perfmon[.]exe
• SSPICLI[.]dll
• Clean[.]bat
• Runex[.]bat
• PO-1109017834665[.]xlsx[.]html
• PO-1109017834665[.]xlsx[.]rar
• PO-1109017834665[.]xlsx[.]exe

MD5

• 3ac401065eb9d48059c49dcdf33d2ca5
• 59e3864ca11e225e3aaa45563e79366a
• d1b75a294c1a2587597f72219d83eadb
• 1dc7995611e26f0e9115a6cd24f0fd1a
• 53498948bc156c8668d68069a73b3dd0
• 03553ce35dfbcabb3ab0b97bd736dbc2
• 0ebe2999e11aef84f3ffd5214f229947
• cef35f9517245d69437ef388ba63ab0f
• 0d897eb9c40f5f595119e5ecb26df68e

SHA-256

• 1e922165e003afe690f81475c957c3812e0f259ea096d227c6d83a8e74b9a83b
• 27b1d8628d1c3d7757c86044b9108a1531d92409f012c45c015eda488df11962
• 2dc4b6bb83457434e26df3164a9099e4177dd98c967d1ea76f3a3d1a2de8d0c6
• 38645d831c28a61afe81fd8c1a786a87ec10ca5059aac03c1f588dace99b5701
• 51dde941670399254ca3480ba22e8ea2aab6854f1ea52e519b28dc2e8d1c66ec
• 83ab486dcd157c14d78e8ba26a8ef4ced34eab344fff1d88558907474dff2d6a
• a26c8cb3853fb5aaeb9a55bacd6eb452a42b0643b6fa8a9a2fc699b41ae51330
• ab60d9d83563c90a10ddec762c39790300afcd4455d029eb6fa5e5c999478870
• b00aedd64879c414c0cb28b3157be35c4a2ef66e5e93f47cbd65cab5810e4e6b
• ead64a6e6cddf7f33f5f7f6b03236e395c2a6d2f94af85112b94c426b247354c
• 119704c353d172f06cf512500e42c94e7c8df9635d462ea0e92b45366f444466
• 0fc72c2cb306f98c12477023d3f7ac2e77948707cb1920b93c98949c2d5a38f9
• 09a5bd9a06840dfb8560ff097505d86d77af1f08877601893262bf14c58c43c5
• 64c812b78b0085eb9d04b66e5872bdbacdc230b0c29a0bd13b71190f3e610dd0

SHA1

• c3b54681e8ac61e605bd399ac680ac15b5608033
• 9742aebce253bfcf3819e28fd5e6ca1e58c10bbf
• 92c8d3dc444e9e6c3b1a7cf94dbee02e4c7bda00
• a224db9e9f2f347587dc398cb898057ce50326f5
• aada5c5af3232a16f7906307326673c5749e3bbb

URL

• http[:]//checker[.]rneiko-elec[.]com
• http[:]//checker[.]rneiko-elec[.]com/
• http[:]//checker[.]rneiko-elec[.]com[:]11012/
• http[:]//checker[.]rneiko-elec[.]com[:]11012

Remediation

• Block the threat indicators at their respective controls.
• Do not respond to unexpected emails.
• Do not download unexpected email attachments and do not click on URLs attached in untrusted emails.