Emotet banking Trojan has been around since 2014 as banking malware. As the software was changed, the developers added additional spamming and malware delivery services found in other
banking malware. Key to Emotet is how it incorporates functionality allowing the software to evade detection by antimalware products.
Emotet also uses Worm-like capabilities to help spread to other connected computers. Because of
this, the Department of Homeland Security (DHS) concludes that Emotet malware is one of the most costly and destructive pieces of malware out there. Emotet spreads on a connected network using a list of common passwords in a brute-force attack. The primary off network propagation mechanism used by Emotet is spam laced with malware. By 2018 newer versions included stealth, new targets, and the ability to install other malware such as ransomware onto infected machines. This was the cause of the July 2019 Lake City, Florida ransomware attack.
Malwarebytes Labs reported a botnet-driven spam campaign in September of 2019 where opening the infected attached Microsoft Word document initiates a macro which downloaded Emotet. A key functionality to Emotet is the ability to deliver custom modules or plugins suited for specific tasks such as stealing Outlook contacts or spreading over a LAN.
Binary Defense has identified a new functionality that uses the wlanAPI interface to enumerate all Wifi networks in the area, and then attempts to spread to these networks and infect all devices that
it can access. With this new propagation method, if a nearby Wi-Fi-capable host is infected, it can attack another Wifi using the same brute-force weak password attacks used on a local network. Zdnet summarized the Wifi spreader’s modus operandi nicely as follows: Once a host is infected Emotet downloads and runs the Wi-Fi spreader module. The Wi-Fi spread-er module lists all Wi-Fi devices enabled on the host and extracts a list of all the locally reachable Wi-Fi networks. The module then performs a brute-force attack on each Wi-Fi network by using two internal lists of easy-to-guess passwords. If the brute-force attack succeeds, the Emotet Wifi spreader now has direct access to another network and moves into a second brute-force attack attempting to guess the usernames and passwords of servers and computers connected to this Wifi network much like a connected network attack. If this second brute-force attack succeeds, Emotet begins its infection cycle again widening its reach.
The Cybersecurity and Infrastructure Security Agency (CISA) has issued a warning on the increased activity related to targeted Emotet attacks roughly two weeks ago, advising admins and users to review the Emotet Malware alert for guidance. Fortunately, all it takes to stop the malware’s spread is having effective passwords on your infrastructure, hosts, and accounts. Emotet will thrive on users who don’t use such good passwords, or who never changed the factory-default access pass-words when they set up their routers.