A coordinated global law enforcement operation has disrupted the infrastructure of Emotet, one of the world's most dangerous botnets and a vector for malware and ransomware attacks.
Participating authorities include Europol, the FBI, and the UK's National Crime Agency, along with agencies from Canada, France, Germany, Lithuania, the Netherlands, and Ukraine, Europol reports. The collaborative effort led investigators to take control over Emotet's infrastructure.
It was a massive feat: The botnet involved several hundred servers located around the world, all of which had different functionalities in order to manage the computers of infected victims, spread to new targets, serve other criminal groups, and strengthen its global network. Emotet affected more than 1.6 million victim computers and caused hundreds of millions of dollars in damage, the Department of Justice reports.
As part of their operation, law enforcement and judicial authorities "gained control of the infrastructure and took it down from the inside," Europol officials write in a statement. "The infected machines of victims have been redirected towards this law enforcement-controlled infrastructure," they say.
Emotet was discovered as a banking Trojan in 2014 but evolved over the years as its operators learned how they could sell to other criminals. It became distributed through an attacker-controlled botnet, which provided more leeway and agency for malware campaigns. These attacks were typically distributed in high volume via malicious emails, says Proofpoint threat intelligence lead Chris Dawson, who notes some campaigns sent millions of messages per day.
"What makes Emotet particularly dangerous for organizations is that it has been the primary base for the future deployment of other banking Trojans and tools used to deploy targeted ransomware attacks," Dawson says.
Operators used a variety of lures to convince victims to open malicious attachments; Emotet emails have appeared as invoices, shipping notices, and COVID-19 information. A malicious Word file may appear attached to an email, or it may be downloaded by clicking a link. Victims who did this would be asked to "enable macros"; doing so would install Emotet on their device.
Emotet grew to exist in several different versions and incorporates a modular design, which made it difficult for defenders to identify and block. Some iterations of Emotet stole banking credentials and sensitive enterprise data, which attackers could threaten to publish. Operators used command-and-control servers to receive updates so they could then adjust their code; Emotet's polymorphic nature meant its code frequently changed.
The botnet's infrastructure acted as a "primary door opener" for computer systems around the world, Europol says. Once attackers had a foothold, their access was sold to other criminals who could then bring banking Trojans, info stealers, or ransomware onto a target machine.
"By specializing in overcoming challenges, to gaining initial access and then selling access to others, this group enabled serious cybercrime around the world and pushed ahead the success of global crime enterprise," says Kaspersky researcher Kurt Baumgartner.
The Dutch National Police, while investigating Emotet, discovered a database containing email addresses, usernames, and passwords stolen by the botnet. Individuals can access its website to determine if their information has been affected.
Gone for Good?
The DoJ reports that foreign law enforcement officials, in collaboration with the FBI, gained access to Emotet servers located overseas and identified the IP addresses of about 1.6 million machines around the world that had been infected with the malware between April 1, 2020 and Jan. 17, 2021. More than 45,000 of these infected devices appear to be located in the US, they report.
Officials replaced Emotet malware on servers in their jurisdiction with a file created by law enforcement, the DoJ report states. Their idea was that computers infected with Emotet would download the new file during a pre-scheduled Emotet update. The file created by law enforcement prevents Emotet operators from communicating with infected devices; however, officials note it does not remediate other malware present on a machine. It's designed to block additional malware from being installed on a computer by breaking its connection with the botnet.
Following the takedown, devices infected with Emotet will be redirected to infrastructure controlled by law enforcement. This will limit the spread of Emotet as operators won't be able to sell access to machines.
It seems officials will take further action to eliminate Emotet. A new report from ZDNet states authorities in the Netherlands plan to mass-uninstall Emotet from infected hosts later this year; two of its three primary C2 centers are located within the country's borders, officials report.
Given the extent of these takedown operations, there is a chance Emotet won't resurface. But it wouldn't be the first time a botnet survived major disruption efforts — Trickbot managed to continue operating following a coordinated effort to eliminate its infrastructure last year.
Baumgartner says it "remains to be seen" whether this is effective in the long term. Ukrainian law enforcement released a video of officers raiding an apartment and seizing attackers' assets as part of their operation, and he says this will have a more severe impact.
"However, we don't know how many parts of this group remain out of reach of cooperating law enforcement groups, so we don't know if the heads of the organization will potentially rebuild with new technical and operations staff within weeks or months," he explains. Officials will need to see how much infrastructure remains intact, as there may be risk of further damage.
Instead of other criminals replacing this group, Baumgartner anticipates it's more likely that new staff will be recruited and their efforts rebuilt. There is a smaller chance another group will emerge to recreate Emotet's techniques and connections within the criminal community.
While the takedown is good news for the security community, Dawson urges companies to not let their guard down. He advises updating security protocols for any future changes and raising security awareness about threats like Emotet. Europol, similarly, advises updating antivirus and operating systems, and avoiding opening attachments from unknown senders.
"If a message seems too good to be true, it likely is and emails that implore a sense of urgency should be avoided at all costs," officials say.