Nemty Ransomware Expands Its Reach, Also Delivered by Trik Botnet

by certadmin

A look into how Trik spreads Nemty, as well as some key updates made to the latest version of the ransomware.
The Nemty ransomware (Ransom.Nemty), initially detected in August 2019, has increased its reach by partnering up with the Trik botnet (Trojan.Wortrik), which now delivers Nemty to compromised computers.
Trik, also known as Phorpiex, has been around for approximately 10 years. In its early days, the malware self-propagated via removable USB drives, Windows Live Messenger, or Skype private messages. The criminals behind the botnet use the infected computers to send email spam and have been observed pushing out a wide range of malware families, with Nemty being the latest to join the list.

Nemty, meanwhile, first appeared on the scene in mid-August 2019. While the malware first appeared to be a run-of-the-mill ransomware, a constant series of changes to the threat made it apparent that it was very much a work in progress and something to be taken seriously.

In the past, Nemty has been observed being spread via the RIG exploit kit, as well as via malicious spam campaigns targeting users in Korea and China, where the malware is attached inside an archive.

Figure 1. Fake résumé-themed Korean malicious spam containing Nemty in the attachment
Figure 1. Fake résumé-themed Korean malicious spam containing Nemty in the attachment

Our data shows that most Nemty infections are found in Korea and China.

Figure 2. Nemty infections by country
Figure 2. Nemty infections by country

In early October, we noticed that Trik had begun distributing Nemty as a payload, adding another channel for the ransomware’s delivery.

How Trik spreads Nemty using the SMB protocol

We observed a recent version of Trik delivering a tiny component that uses the Server Message Block (SMB) protocol and a list of hardcoded credentials to try to connect to remote computers with port 139 open.

First, the SMB component creates the following registry entry:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List\”[PATH OF THE ORIGINAL FILE]” = “[PATH OF THE ORIGINAL FILE]:*:Enabled: Windows NetBIOS Driver”

Trik then checks if the file winsvcs.txt is present or not in the %AppData% directory on the compromised computer. This file is present if the computer has previously been infected with Trik.

  • If winsvcs.txt is not present, the Nemty ransomware is downloaded and executed. This check prevents Trik from being hindered by files on the computer being encrypted by Nemty.
  • If winsvcs.txt is present, the SMB component checks if it is running as a service or not.
    • If it is not running as a service, the component tries to spread itself through the SMB protocol.
Figure 3. SMB component either downloads Nemty from a C&C server or spreads itself to other computers
Figure 3. SMB component either downloads Nemty from a C&C server or spreads itself to other computers

To find targets, the SMB component generates random IP addresses then tries to connect to them on port 139.

Figure 4. Trik’s SMB component generates random remote IP addresses to connect to
Figure 4. Trik’s SMB component generates random remote IP addresses to connect to

From analysing the malware’s code, we can see that it skips the routine if the created IP address is a local one (Figure 4). The malware can infect public IP addresses with port 139 open that are using any of the common administrator usernames and passwords on its list.

Usernames: Administrator, administrator, Admin, admin

Passwords: 123, 1234, 12345, 123456, 1234567, 12345678, 123456789, 1234567890, 123123, 12321, 123321, 123abc, 123qwe, 123asd, 1234abcd, 1234qwer, 1q2w3e, a1b2c3, administrator, Administrator, admin, Admin, admin123, Admin123, admin12345, Admin12345, administrator123, Ad ministrator123, nimda, qwewq, qweewq, qwerty, qweasd, asdsa, asddsa, asdzxc, asdfgh, qweasdzxc, q1w2e3, qazwsx, qazwsxedc, zxcxz, zxccxz, zxcvb, zxcvbn, passwd, password, Password, login, Login, pass, mypass, mypassword, adminadmin, root, rootroot, test, testtest, temp, temptemp, foofoo, foobar, default, password1, password12, password123, admin1, admin12, admin123, pass1, pass12, pass123, root123, abc123, abcde, abcabc, qwe123, test123, temp123, sample, example, internet, Internet

If access is granted, the malware uses the SMB protocol to copy itself to the remote machine. It then uses the Windows Service Control Manager to start the SMB component’s process on the remote machine. The sample running on the remote machine also checks for the presence of winsvcs.txt, which again determines whether or not Nemty is downloaded and executed.

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To read the original article:

https://www.symantec.com/blogs/threat-intelligence/nemty-ransomware-trik-botnet

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