Retadup Worm Squashed After Infecting 850K Machines

An operation involving French law enforcement, the FBI, and Avast forces Retadup to delete itself from victim machines.

Retadup, a malicious worm that infected more than 850,000 Windows machines, has been taken down by an international operation involving the French National Gendarmeries Cybercrime Fighting Center (C3N), US Federal Bureau of Investigation, and security firm Avast.
The worm was first
exposed
by Trend Micro back in 2017, when it was spotted targeting Israeli hospitals and stealing information. A few months later, another Retadup variant was seen targeting industries and governments in South America. Two years later, Avast analysts are sharing details of a separate campaign in which victim machines were targeted with a cryptocurrency miner.
Avast researchers began to closely monitor Retadup activity in March 2019, when malicious Monero cryptocurrency miner XMRig caught their eye with its advanced abilities to bypass detection. Further investigation into the distribution of XMRig led them to Retadup, the worm being used to deliver XMRig to machines mostly in Spanish-speaking countries in Latin America.
Retadup primarily spreads by dropping malicious LNK files onto connected drives. It iterates over all connected drives where the assigned letter is not c, goes through all the folders in the root folder of a selected drive, and for each one creates an LNK file to mimic the real folder and trick victims into clicking it. When executed, the malicious LNK file will run the malicious script. Neither Avast nor Trend Micro researchers have determined the infection vector for XMRig.
XMRig doesnt use all of a CPUs power when it mines cryptocurrency, says Avast malware researcher Jan Vojtesek. This helps it fly under the radar. Victims whose machines are running a fully powered cryptominer will notice their machines slow down, he explains. The malware also avoids mining when taskmgr.exe is running, so its difficult to detect raises in CPU usage.
In addition to XMRig, researchers noticed instances of Retadup distributing Stop ransomware and Arkei password stealer. The ransomware seemed to be a test trial, Vojtesek says. They probably were trying to figure out how much they could make from ransomware.
Closer analysis of Retadup showed its command-and-control (C2) communication infrastructure was quite simple, Vojtesek explains
in a report
. Analysts identified a design flaw in the C2 protocol that enabled them to remove Retadup from infected machines if they assumed control over the C2 server, he explains. By doing this, they could purge XMRig from victims devices without asking them to do anything. Theyd simply need to connect to the server to destroy the threat.
Setting Up the Takedown
Because most of Retadups C2 infrastructure was located in France, Avast contacted the French National Gendarmerie to share their research and proposed disinfection strategy of abusing the flaw in the C2 server to neutralize the attack campaign.
We spent some time analyzing the threat, Vojtesek says. Only after we were confident it could actually be disinfected, and we had a solid plan on how to carry out the disinfection, then we contacted them.
While French law enforcement presented the strategy to the prosecutor, Avast continued to analyze Retadup. Researchers tested the disinfection process, discussed potential risks, and reviewed a snapshot of the C2 servers disk obtained by the Grandarmerie that did not contain victims data. Attackers sent a great deal of data about infected to the machines to the C2 server; researchers learned the exact amount of infections and geographical locations.
The teams got the go-ahead to launch their disinfection operation in July 2019 and replaced the malicious C2 server with a disinfection server that made connected instances of Retadup self-destruct. When bots connected to the server, the disinfection server responded and destroyed. So far it has neutralized more than 850,000 devices that connected to the attackers C2 server.
Some parts of the C2 infrastructure were located in the US, so the Gendarmerie alerted the FBI, which took those down. By July 8, Retadups authors no longer had control over the malware. Because infected machines received orders from the C2 server, they no longer had new jobs, meaning they were unable to continue stealing victims power to fuel their monetary gain.
Related Content:
7 Biggest Cloud Security Blind Spots
Facebook Patches Second Account-Takeover Flaw in Instagram
Magecart Shops for Victims as E-Commerce Market Grows
The Right to Be Patched: How Sentient Robots Will Change InfoSec Management
Check out
The Edge
, Dark Readings new section for features, threat data, and in-depth perspectives. Todays top story:
Fuzzing 101: Why Bug-Finders Still Love It After All These Years
.

Last News
▸ ArcSight prepares for future at user conference post HP acquisition. ◂ Discovered: 07/01/2025 Category: security	▸ Samsung Epic 4G: First To Use Media Hub ◂ Discovered: 07/01/2025 Category: security	▸ Many third-party software fails security tests ◂ Discovered: 07/01/2025 Category: security

**Cyber Security Categories**
Google Dorks Database	Exploits Vulnerability	Exploit Shellcodes

CVE List

Tools/Apps

News/Aarticles

Phishing Database

Deepfake Detection

Trends/Statistics & Live Infos

Tags:
Retadup Worm Squashed After Infecting 850K Machines