Analysis by: Jemimah Mae Molina


Perl/Shellbot.NAK trojan (NOD32); Troj/PerlShel-C (SOPHOS_LITE)


Windows, Unix, Linux


  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes


Infection Channel: Downloaded from specific site

This backdoor comes bundled with a Monero miner, both spread by a botnet. The techniques employed are reminiscent of the Outlaw hacking group that Trend Micro reported in November 2018.

This Backdoor connects to Internet Relay Chat (IRC) servers. It joins an Internet Relay Chat (IRC) channel.


File Size: 35,116 bytes
File Type: PL
Memory Resident: Yes
Initial Samples Received Date: 28 May 2019
Payload: Connects to URLs/IPs

Arrival Details

This Backdoor may be downloaded from the following remote site(s):

  • http://{BLOCKED}.{BLOCKED}.70.249/.x15cache

Backdoor Routine

This Backdoor connects to any of the following Internet Relay Chat (IRC) servers:

  • {BLOCKED}.{BLOCKED}.171.227:443

It joins any of the following Internet Relay Chat (IRC) channels:

  • #007

It accesses a remote Internet Relay Chat (IRC) server where it receives the following commands from a remote malicious user:

  • IRC Control:
    • join → join a specified channel
    • part → leave a specified channel
    • rejoin → leave then rejoin a specified channel
    • op → grant a user an operator status
    • deop → revoke a user's operator status
    • voice → grant a user a voice status
    • devoice → revoke a user's voice status
    • msg → send a private message
    • flood → send a private message for a specified number of times
    • ctcpflood → send a client-to-client protocol request to a specified user or channel for a specified number of times
    • ctcp → send a client-to-client protocol request to a specified user or channel
    • invite → invite a user to join a specified channel
    • nick → change nickname
    • conecta → connect to a specified server
    • send → establish a direct connection with another user
    • raw → toggles raw events processing
    • eval → execute specified command
    • entra → join a channel after random seconds
    • sai → leave a channel after random seconds
    • sair → disconnect from the server
    • novonick → change nickname to x{random number}
    • estatisticas → toggles statistics flag
    • pacotes → toggles packets flag
  • Scan ports 21, 22, 23, 25, 53, 80, 110, 143, 6665 of a specific IP
  • Download a file
  • Scan open ports of a specific hostname
  • UDP Flooding
  • Connect to an arbitrary socket
  • Simultaneous IGMP, ICMP, UDP and TCP flooding on open ports with statistic report


Minimum Scan Engine: 9.850
VSAPI OPR PATTERN File: 15.139.00
VSAPI OPR PATTERN Date: 29 May 2019

Step 1

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 users must disable System Restore to allow full scanning of their computers.

Step 2

Scan your computer with your Trend Micro product to delete files detected as Backdoor.Perl.SHELLBOT.AB. 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:

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