Brinztech Alert: The Alleged RustDesk Checker and Bruteforce Tool is on Sale

Dark Web News Analysis

The dark web news reports the sale of a sophisticated, custom-made offensive tool targeting RustDesk, a popular open-source remote desktop application. A threat actor on a hacker forum is selling a RustDesk ID Checker and Brute-force Tool.

The tool is advertised as highly performant, capable of checking the online/offline status of RustDesk IDs at a rate of 800 checks per second. More alarmingly, the brute-force module can run up to 1,000 concurrent threads to guess passwords for active IDs. The seller is asking $5,000 USD for the full package (or $3,000 for one of two copies) and includes the Source Code, allowing the buyer to modify the malware.

Key Cybersecurity Insights

Tools that weaponize legitimate remote administration software are “Tier 1” access threats because they blend in with normal administrative traffic:

• Industrialized Brute-Forcing: The capability to run 1,000 threads transforms a simple password guessing attempt into a mass casualty event. Attackers can scan entire IP ranges or ID blocks to find weak targets in minutes, rather than days.
• Weaponizing Legitimate Tools (LotL): RustDesk is a legitimate tool used by IT admins. By using a specialized brute-forcer, attackers can gain access via a trusted application, often bypassing antivirus software that would flag a standard Trojan or Rat.
• Source Code Danger: The sale of the Source Code is the most critical aspect. It allows sophisticated buyers to refactor the code, change its signature to evade detection, or integrate it into larger automated attack frameworks (botnets).
• Initial Access Brokerage: This tool is designed for Initial Access Brokers (IABs). They use it to hijack thousands of desktops, which are then sold in bulk to ransomware gangs who use the access to deploy encryption payloads.

Mitigation Strategies

To protect your remote access infrastructure, the following strategies are recommended:

• Mandatory MFA: You must enforce Multi-Factor Authentication (MFA) for all RustDesk connections. A brute-force tool can guess a password, but it cannot guess a dynamic 2FA code.
• Self-Hosting: If using RustDesk, consider self-hosting the rendezvous server rather than using public infrastructure. This allows you to restrict access to only known company IP addresses.
• Rate Limiting: Implement strict rate limiting on the network firewall to detect and block the high-volume traffic (800 checks/second) generated by this tool.
• Password Complexity: Enforce long, complex passwords. With 1,000 threads, short passwords will be cracked almost instantly.

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