Letgo Infostealer actively spreading in the wild.

November 22, 2017

The SonicWall Capture Labs Threat Research Team observed reports of a new variant family of Letgo Malware [Letgo.A] actively spreading in the wild.

The Malware gathers confidential information from the computer such as login details, passwords; financial information sends it to its own C&C Server.

Infection Cycle:

The Malware adds the following files to the system:

  • Malware.exe

    • %systemroot%Fonts22.bat [ Batch File ]

    • %systemroot%Fonts6.vbs [ VB Script File ]

    • %systemroot%FontsExit.exe

      • Responsible for running Command on target machine.

    • %systemroot%FontsLetGo.exe [Service ServiceTshcwt]

      • Install Service on target machine.

    • %systemroot%FontsFaker.exe [Service ServicetyfdYEw]

    • %systemroot%Fontsrestart.reg [ Registry files ]

    • %systemroot%FontsSoul.exe

      • Responsible for sending data to C&C server.

The Malware adds the following keys to the Windows registry to ensure persistence upon reboot:

Once the computer is compromised, the malware copies its own executable file to Systemroot folder and runs following commands:

A user's data can be very valuable for an attacker, thereby more data translates to more profit. The main goal of this malware is to get as much user data as possible.

The Malware performs user land hooks for the following functions:

Command and Control (C&C) Traffic

Letgo.A performs C&C communication over port 443. The malware sends a victim's system information

to its own C&C server via following format, here are some examples:

SonicWall Gateway AntiVirus provides protection against this threat via the following signature:

  • GAV: Letgo.A (Trojan)

  • GAV Cloud Id: 59515096) UWtrojan (Trojan)