Asaf Dahan, senior director at Cybereason, is trying to explain what happened.
"My team and I were monitoring the threat landscape across different regions, industries, and technologies. We were chasing a lead on different malware and went down a rabbit hole. And when you go down a rabbit hole, you can become distracted," he says.
The distraction at the bottom of the rabbit hole turned out to be EventBot, a banking Trojan being built in real time as the team watched.
Dahan is in charge of the Cybereason Nocturnus research team. What he and his team found in March was a new type of Android malware that targets users of more than 200 different financial applications and is getting better on an almost-daily basis.
"It was very interesting because it looked like it was still under development — version zero-dot-something. We saw a banking Trojan in the making," Dahan says.
In a blog post about its research, the Nocturnus team says EventBot abuses Android's accessibility features to steal user data from financial applications, read user SMS messages, and steal SMS messages to allow the malware to bypass two-factor authentication. The team has watched as the developer (or developers) of EventBot has improved it step by step across a couple of months, Dahan says.
"We saw that whoever is behind it was uploading and trying to test detection, and every few days we got new samples from VirusTotal and other sources. Every few days the threat actor would update the code with new features, new obfuscation, and new tools," he explains.
While EventBot is becoming more capable, it has not yet been fully operationalized, Dahan says. It has not yet appeared on Google Play or another legitimate Android app store; Dahan hopes that by identifying the malware now, it will be prevented from taking hold on a major app store.
Indeed, prevention will be critical, Dahan says, because without it he sees the potential for EventBot to become a major banking Trojan and info stealer, on a par with the Raccoon stealer that was a major piece of Android malware in 2019. The Nocturnus team has already found a number of legitimate application icons associated with EventBot — icons that the malware could use to hide its true identity from victims.
While the researchers have watched EventBot grow, there's still a great deal they don't know about the malware — such as the identity of the developer.
"We haven't seen significant code overlap with previous actors, so it's likely to have been written from scratch," Dahan says. "It could be a new threat actor or someone existing who decided to try new malware. I don't think they're super-experienced, but they're not novice — they're somewhere in between."
There's also not enough information to know precisely how EventBot will be used in attacks, whether by the developer as proprietary code or in a malware-as-a-service leasing scheme.
"This could be both — it depends on the size of the operation and the connections the threat actor has," Dahan says. "The criminal cyber ecosystem is vast and complicated, and reputation and trust are your strongest currencies."
Dahan says his team will be watching EventBot as it continues to develop, but he does have advice on protection for potential victims.
"This is an Android threat, not iOS. We haven't seen the malware on Google Play, so it's most likely in the first stages to be available in the rogue stores or dubious sites offering free cracked apps," Dahan says, pointing out that these dubious sites are the sources of a large percentage of the malware found on Android devices. Individuals should not get their apps from any site not created and maintained by a legitimate business, he advises.
"[Next], in order for this to work it requires the user to authorize or give permission for the accessibility features," Dahan says. Users should apply critical thinking to any app requests for access to microphones, cameras, cloud accounts, or other data sources.
"If the app is requesting permission it doesn't really need, don't click 'yes,'" he says. "Even legitimate apps that harvest a lot of data and turn us into the product should be watched. Be very mindful of the permissions the app is asking you for."
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