In a troubling development for organizations, security researchers are reporting a recent resurgence in activity related to Emotet — malware that the US Department of Homeland Security (DHS) has previously described as among the most destructive ever.
Cisco Talos on Thursday reported seeing increased Emotet activity targeting US military domains and domains belonging to state and federal governments.
According to the vendor, the operators of Emotet appear to have successfully compromised accounts of one or more people working for or with the US government and sent out spam emails containing the malware to their contacts. The result was a rapid increase in the volume of messages containing Emotet directed at .mil and .gov top-level domains last month and and so far this month, the vendor said.
Researchers at Cofense, meanwhile, reported on another Emotet campaign, this one targeted at some 600 staffers at the United Nations. The campaign involved an email purporting to be from the Permanent Mission of Norway with an attachment that, if opened, would eventually result in Emotet being downloaded on the system.
Jason Meurer, senior research engineer at Cofense, says there has been at least two previous compromises of a permanent mission to the United Nations related to Emotet, which may have been used to gather contact lists and emails. "We saw a few other subject lines that appear to have been scraped from stolen emails, likely indicating more victims leading up to this most recent campaign," he says.
In late December, Check Point Software described its incident response team as seeing hundreds of Emotet attacks per day, including one on the city of Frankfurt that forced officials to take its network offline to prevent further damage. According to the company, it responded to some 34 attacks last year where Emotet had been used to infect a network with Ryuk ransomware. Every single Ryuk ransomware incident that Check Point investigated in 2019, in fact, involved Emotet, Check Point said.
Emotet emerged in 2014 as a banking Trojan, but over the years has morphed into one of the most sophisticated and widely used tools for distributing malware. Its operators are known for infecting systems widely and then selling access to those systems to other threat actors, most notably those behind the Trickbot banking Trojan and the Ryuk ransomware family.
Emotet spreads mainly via spam email — often customized to appear more convincing to targeted victims. The malware is typically concealed in PDF documents, malicious links, or rogue Word documents. Typical lures to get users to click on the attachments and links have included names suggesting PayPal receipts, shipping notifications, invoices for payments, and legal documents. The recent campaign targeting UN staffers involved an attachment that purported to be some kind of a signed agreement involving the Norwegian government.
Once Emotet infects a system, it steals names and email addresses from victims' contact lists and uses them to send phishing emails to other victims. It can also steal passwords and comes integrated with features for detecting sandboxes and other security-control mechanisms. Emotet campaigns have hit organizations around the world, but among the most heavily targeted are those based in North America, the UK, and Australia.
"Getting infected with Emotet has many different ripple effects," says Craig Williams, director of outreach at Cisco Talos. "Infected systems are used to transmit Emotet to additional victims, sensitive information such as email data can be exfiltrated, and the infection gives attackers the ability to move laterally within networks where Emotet is present."
What makes Emotet especially troubling is the way it uses social engineering and personal and professional relationships to spread, Cisco Talos said in its report on the recent attacks against .mil and .gov targets. Because Emotet uses a victim's contact list to send itself to other people, a person receiving the email can be lured into believing it is safe. Sometimes the message that Emotet sends includes the contents of a previous email exchange between the victim and the recipient, further adding to its apparent authenticity, Cisco Talos said.
Remediating Emotet infections can be challenging because of how adept the malware is at spreading inside a network — from a single machine to hundreds, Williams says. "Additionally, it has been used in some large-scale ransomware campaigns that have resulted in large amounts of data loss and destruction," he says.
Security researchers and others have been especially worried about Emotet's use in distributing other malware and in providing access to infected networks. Back in June 2018, the DHS's Cybersecurity and Infrastructure Security Agency (CISA) had described Emotet as "among the most costly and destructive malware" targeting government, public, and private-sector organizations. According to CISA, each Emotet infection has cost state, local, and federal government entities up to $1 million to remediate.
CISA has warned about the polymorphic nature of the malware and its ability to continuously evolve and update its functions, as well as its ability to evade typical signature-based detection systems and to maintain persistence on an infected system.
Since the 2018 CISA alert, security researchers have said the malware and methods used to distribute it have only become more devious and dangerous.
"Emotet has established itself as a king amongst malware distributors, capable of delivering infections to a large number of infected hosts," Check Point said in a report released this week. "It is also able to act as a launching platform for precise and coordinated attacks against well-financed organizations."
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