Exchange servers first compromised by Chinese hackers hit with ransomware

As if Exchange users didn’t already have enough to worry about, they have this

Organizations using Microsoft Exchange now have a new security headache: never-before-seen ransomware that’s being installed on servers that were already infected by state-sponsored hackers in China reported ArsTecnica

Microsoft reported the new family of ransomware deployment late Thursday, saying that it was being deployed after the initial compromise of servers. Microsoft’s name for the new family is Ransom: Win32/DoejoCrypt.A. The more common name is DearCry.

We have detected and are now blocking a new family of ransomware being used after an initial compromise of unpatched on-premises Exchange Servers. Microsoft protects against this threat known as Ransom:Win32/DoejoCrypt.A, and also as DearCry.

— Microsoft Security Intelligence (@MsftSecIntel) March 12, 2021

Piggybacking off Hafnium

Security firm Kryptos Logic said Friday afternoon that it has detected Hafnium-compromised Exchange servers that were later infected with ransomware. Kryptos Logic security investigator Marcus pedagogue told Ars that the ransomware is DearCry.

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“We’ve simply discovered 6970 exposed web shells that are in public exposed and were placed by actors exploiting the Exchange vulnerability,” Kryptos Logic said. “These shells are getting used to deploy ransomware.” Web shells are backdoors that permit attackers to use a browser-based interface to run commands and execute malicious code on infected servers.

We’ve just discovered 6970 exposed web shells which are publicly exposed and were placed by actors exploiting the Exchange vulnerability. These shells are being used to deploy ransomware. If you’re signed up to Telltale (https://t.co/caXU7rqHaI) you can check you’re not affected pic.twitter.com/DjeM59oIm2

— Kryptos Logic (@kryptoslogic) March 12, 2021

Anyone who is aware of the uniform resource locator to at least one of those public web shells will gain complete management over the compromised server. The DearCry hackers are exploiting these shells to deploy their ransomware. The web shells were at the start put in by Hafnium, the name Microsoft has given to a state-sponsored threat actor operational out of China.

Hutchins aforementioned that the attacks are “human-operated,” which means a hacker manually installs ransomware on one Exchange server at a time. Not all of the nearly 7,000 servers are hit by DearCry.

“Basically, we’re setting out to see criminal actors exploitation shells left behind by metal to induce a footing into networks,” pedagogue explained.

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The readying of ransomware, which security specialists have said was inevitable, underscores a key side regarding the continued response to secure servers exploited by ProxyLogon. It’s not enough to easily install the patches. while not removing the web shells left behind, servers stay receptive to intrusion, either by the hackers who originally put in the backdoors or by different fellow hackers who understand the way to gain access to them.

Little is understood regarding DearCry. Security firm Sophos said that it’s supported a public-key cryptosystem, with the general public key embedded within the file that installs the ransomware. which enables files to be encrypted while not the requirement to first connect with a command-and-control server. To decipher the data, victims’ should acquire the non-public key that’s known solely to the attackers.

What you need to know about #DearCry by Mark Loman (@markloman) Director, engineering technology office, Sophos (a thread):

From an encryption-behavior view, DearCry is what Sophos ransomware experts call a ‘Copy’ ransomware.

1/9

— SophosLabs (@SophosLabs) March 12, 2021

Among the primary to get DearCry was Mark Gillespie, a security professional who runs a service that helps researchers identify malware strains. On Thursday, he reported that starting on Tuesday, he started receiving queries from Exchange servers within the US, Canada, and Australia for malware that had the string “DEARCRY.”

? #Exchange Servers Possibly Hit With #Ransomware ?
ID Ransomware is getting sudden swarm of submissions with “.CRYPT” and filemarker “DEARCRY!” coming from IPs of Exchange servers from US, CA, AU on quick look. pic.twitter.com/wPCu2v6kVl

— Michael Gillespie (@demonslay335) March 11, 2021

He later found somebody posting to a user forum on Bleeping pc locution the ransomware was being put in on servers that had initially been exploited by Hafnium. Bleeping pc soon confirmed the hunch.

John Hultquist, a vice chairman at security firm Mandiant, aforementioned piggybacking on the hackers who installed the web shells may be a quicker and a lot of economical means that to deploy malware on unpatched servers than exploiting the ProxyLogon vulnerabilities. And as already mentioned, notwithstanding servers are patched, ransomware operators will still compromise the machines once web shells haven’t been removed.

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“We are anticipating a lot of exploitation of the exchange vulnerabilities by ransomware actors within the close to term,” Hultquist wrote in an email. “Though several of the still unpatched organizations could are exploited by cyber undercover work actors, criminal ransomware operations may cause a larger risk as they disrupt organizations and even extort victims by emotional purloined emails.”

Update 7:40 pm EST: This post was updated to get rid of “7,000” from the headline and to create clear not all of them have been infected with ransomware.