The notorious Emotet botnet, which has been used in extensive attacks on companies around the globe for many years, has been taken down as part of a coordinated effort by Europol, the FBI, the UK National Crime Agency, and other law enforcement agencies.

The threat actors behind Emotet used their malware to create a backdoor in the systems of many companies, with access then sold to other threat groups to conduct further malicious activities including stealing sensitive data and extortion through the deployment of ransomware.

The operation has been planned for around two years and was coordinated to ensure that the multi-country infrastructure was simultaneously taken down to disrupt any attempts by the threat group to reconstruct the network. Law enforcement agencies have seized control of hundreds of servers and have taken control of the entire Emotet infrastructure, in what will be seen by many to be the most important malware takedowns to date. The takedown has prevented the Emotet gang from communicating with the malware and has resulted in the loss of control of the army of compromised devices that make up the botnet.

Europol and its partners succeeded in mapping the entire infrastructure, took control of the network, and deactivated the Emotet Trojan. A software update was placed on the main servers used to control the malware, two of which were located in the Netherlands. Infected computer systems will retrieve the update, which will see Emotet Trojan on those systems quarantined.

The Most Dangerous Malware and Most Prolific Botnet

Emotet is arguably the most dangerous malware of recent years and the botnet used to distribute it is one of the most prolific. Around 30% of all malware attacks in 2020 involved the Emotet Trojan.

Phishing emails were used to deliver the Emotet Trojan. Massive phishing campaigns were conducted using a wide range of lures to trick recipients into opening malicious attachments or visiting websites that downloaded the Emotet Trojan. The lures used in the campaigns frequently changed, taking advantage of world events to maximize the probability of the attachments being opened.

Emotet started life as a banking Trojan but was later developed to also serve as a malware dropper. Emotet delivered other banking Trojans such as TrickBot as the secondary malware payload, and ransomware variants such as Ryuk – each of which were dangerous in their own right.

Devices infected with Emotet are added to the botnet and used to distribute copies of the Emotet Trojan to other devices on the network and the user’s contacts by hijacking the user’s email account. A single device on a corporate network that was infected with Emotet could quickly result in widespread infection. The Trojan was also particularly difficult to eradicate, as removal of the infection would only be temporary, with other devices on the network simply re-infecting the cleaned device.

In the leadup to the 2020 Presidential election in the United States, Microsoft and its partners succeeded in seizing control of some of the infrastructure used to control and distribute the TrickBot Trojan. In that case the operation was only temporarily successful, as the TrickBot gang was able to rapidly recover and restore its infrastructure.

Time will tell as to how successful the Emotet takedown has been and whether the operation has only temporarily disrupted the activities of the Emotet gang or whether the takedown has left it completely crippled.