Trojan.Linux.SKIDMAP.UWEJY

September 18, 2019
 Analysis by: Henry Alarcon Jr.
 PLATFORM:

Linux

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware


This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

  TECHNICAL DETAILS

File Size:

1,342,085 bytes

File Type:

ELF

File Compression:

UPX

Memory Resident:

No

Initial Samples Received Date:

30 Aug 2019

Payload:

Drops files, Modifies files, Deletes files

Arrival Details

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This Trojan drops the following files:

  • /lib64/security/pam_unix.so -> if 64-bit, compromised pam_unix.so file
  • /lib/x86_64-linux-gnu/security/pam_unix.so -> if 32-bit, compromised pam_unix.so file
  • /etc/rctlconf/certs/rctl_ca.crt
  • /etc/rctlconf/rctlcli.cfg

It drops and executes the following files:

Other Details

This Trojan does the following:

  • It installs LKM (Linux Kernel Module) rootkits in the victim machine and has different versions of the modules for specific kernel versions:
  • It modified all dropped files accessed and modified information to:
    • 02/22/2012
  • It deletes the following files if exist in the affected system:
    • /etc/cron.d/ntp
    • /etc/cron.hourly/ntp
  • It clears the content of the following files by executing the following command:
    • /bin/echo 0 > /var/log/messages
    • /bin/echo 0 > /var/log/kern.log
    • /bin/echo 0 > /var/log/audit/audit.log
  • It checks for the presence of the following files:
    /lib64/security/pam_unix.so
    /lib/x86_64-linux-gnu/security/pam_unix.so.
    If present, it will replace it with a malicious copy of "pam_unix.so", otherwise it will create its own "pam_unix.so"
  • It sets the following configurations:
    SELINUX=disabled
    SELINUXTYPE=targeted, to disabled setenforce

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.346.05

FIRST VSAPI PATTERN DATE:

05 Sep 2019

VSAPI OPR PATTERN File:

15.347.00

VSAPI OPR PATTERN Date:

06 Sep 2019

Step 1

Scan your computer with your Trend Micro product to delete files detected as Trojan.Linux.SKIDMAP.UWEJY. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check the following Trend Micro Support pages for more information:

Step 2

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result. DATA_GENERIC
  • Once located, select the file then press SHIFT+DELETE to delete it.
    *Note: Read the following Microsoft page if these steps do not work on Windows 7 and Windows Server 2008 (R2).

    • Step 3

    Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.


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