Ransomware now attacks Microsoft Exchange servers with ProxyLogon exploits

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New DEARCRY Ransomware is targeting Microsoft Exchange Servers

 

 

Threat actors are now installing a new ransomware called 'DEARCRY' after hacking into Microsoft Exchange servers using the recently disclosed ProxyLogon vulnerabilities.

 

Since Microsoft revealed earlier this month that threat actors were compromising Microsoft Exchange servers using new zero-day ProxyLogon vulnerabilities, a significant concern has been when threat actors would use it to deploy ransomware.

 

Unfortunately, tonight our fears became a reality, and threat actors are using the vulnerabilities to install the DearCry ransomware.

The DearCry ransomware

According to Michael Gillespie, the creator of the ransomware identification site ID-Ransomware, starting on March 9, users began submitting a new ransom note and encrypted files to his system.

 

After reviewing the submissions, Gillespie discovered that users submitted almost all of them from Microsoft Exchange servers.

 

On March 9, a victim also created a forum topic in the BleepingComputer forums where they state their Microsoft Exchange server was compromised using the ProxyLogon vulnerabilities, with the DearCry ransomware being the payload.

 

Post about DearCry on BleepingComputer forums

 

After publishing our story, Microsoft has confirmed that the DearCry ransomware is installed in human-operated attacks on Microsoft Exchange servers using the ProxyLogon vulnerabilities.

 

Microsoft observed a new family of human operated ransomware attack customers – detected as Ransom:Win32/DoejoCrypt.A. Human operated ransomware attacks are utilizing the Microsoft Exchange vulnerabilities to exploit customers. #DearCry @MsftSecIntel

 

— Phillip Misner (@phillip_misner) March 12, 2021

 

MalwareHunterTeam was able to find three samples of this ransomware on VirusTotal [1, 2, 3], all of which are MingW-compiled executables. The one analyzed by BleepingComputer includes the following PDB path:

C:\Users\john\Documents\Visual Studio 2008\Projects\EncryptFile -svcV2\Release\EncryptFile.exe.pdb

According to Advanced Intel's Vitali Kremez, when launched, the DearCry ransomware will attempt to shut down a Windows service named 'msupdate.' It is not known what this service is, but it does not appear to be a legitimate Windows service.

 

Code that shuts down the msupdate service

 

The ransomware will now begin to encrypt the files on the computer. When encrypting files, it will append the .CRYPT extension the file's name, as shown below.

 

DearCry encrypted files

 

Gillespie told BleepingComputer that the ransomware uses AES-256 + RSA-2048 to encrypt the files and prepends the 'DEARCRY!' string to the beginning of each encrypted file.

 

DEARCRY file marker in encrypted file

 

When done encrypting the computer, the ransomware will create a simple ransom note named 'readme.txt' on the Windows desktop. This ransom note contains two email addresses for the threat actors and a unique hash, which Gillespie states is an MD4 hash of the RSA public key.

 

DearCry ransom note

 

For at least one of the victims, the ransomware group demanded a $16,000 ransom.

 

Unfortunately, the ransomware does not appear to have any weaknesses that would allow victims to recover their files for free.

Patch now!

While DearCry is not 100% confirmed to be installed via the Microsoft Exchange ProxyLogon vulnerabilities, there is a good chance that it is based on the information at hand.

 

According to new data shared by cybersecurity firm Palo Alto Networks with BleepingComputer, tens of thousands of Microsoft Exchange servers have been patched over the last three days.

 

Unfortunately, Palo Alto Networks states that there are still approximately 80,000 older servers that cannot directly apply the recent security updates.

“I’ve never seen security patch rates this high for any system, much less one as widely deployed as Microsoft Exchange,” said Matt Kraning, Chief Technology Officer, Cortex at Palo Alto Networks. “Still, we urge organizations running all versions of Exchange to assume they were compromised before they patched their systems, because we know attackers were exploiting these zero-day vulnerabilities in the wild for at least two months before Microsoft released the patches on March 2.”

 

All organizations are strongly advised to apply the patches as soon as possible.

 

Not only to protect your mailboxes from being stolen but now to prevent them from being encrypted.

 

Update 3/11/21: Updated article after confirmation from Microsoft that it is installed via ProxyLogon vulnerabilities.

 

 

Source: New DEARCRY Ransomware is targeting Microsoft Exchange Servers

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Hackers Are Targeting Microsoft Exchange Servers With Ransomware

 

 

It didn't take long. Intelligence agencies and cybersecurity researchers had been warning that unpatched Exchange Servers could open the pathway for ransomware infections in the wake of swift escalation of the attacks since last week.

 

Now it appears that threat actors have caught up.

 

According to the latest reports, cybercriminals are leveraging the heavily exploited ProxyLogon Exchange Server flaws to install a new strain of ransomware called "DearCry."

 

"Microsoft observed a new family of human operated ransomware attack customers – detected as Ransom:Win32/DoejoCrypt.A," Microsoft researcher Phillip Misner tweeted. "Human operated ransomware attacks are utilizing the Microsoft Exchange vulnerabilities to exploit customers."

 

In a joint advisory published by the U.S. Cybersecurity and Infrastructure Security Agency (CISA) and the Federal Bureau of Investigation (FBI), the agencies warned that "adversaries could exploit these vulnerabilities to compromise networks, steal information, encrypt data for ransom, or even execute a destructive attack."

 

Successful weaponization of the flaws allows an attacker to access victims' Exchange Servers, enabling them to gain persistent system access and control of an enterprise network. With the new ransomware threat, unpatched Servers are not only at risk of potential data theft but also get potentially encrypted, preventing access to an organization's mailboxes.

 

 

Meanwhile, as nation-state hackers and cybercriminals pile on to take advantage of the ProxyLogon flaws, a proof-of-concept (PoC) code shared on Microsoft-owned GitHub by a security researcher has been taken down by the company, citing that the exploit is under active attack.

 

In a statement to Vice, the company said, "In accordance with our Acceptable Use Policies, we disabled the gist following reports that it contains proof of concept code for a recently disclosed vulnerability that is being actively exploited."

 

The move has also sparked a debate of its own, with researchers arguing that Microsoft is "silencing security researchers" by removing PoCs shared on GitHub.

 

"This is huge, removing a security researchers code from GitHub against their own product and which has already been patched," TrustedSec's Dave Kennedy said. "It was a PoC, not a working exploit — none of the PoCs have had the RCE. Even if it did, that's not their call on when the appropriate time to release is. It's an issue in their own product, and they are silencing security researchers on that."

 

This was also echoed by Google Project Zero researcher Tavis Normandy.

 

"If the policy from the start was no PoC/metasploit/etc — that would suck, but it's their service," Normandy said in a tweet. "Instead they said OK, and now that it's become the standard for security pros to share code, they have elected themselves the arbiters of what is 'responsible.' How convenient."

 

If anything, the avalanche of attacks should serve as a warning to patch all versions of the Exchange Server as soon as possible, while also take steps to identify signs of indicators of compromise associated with the hacks, given that the attackers were exploiting these zero-day vulnerabilities in the wild for at least two months before Microsoft released the patches on March 2.

 

We have reached out to Microsoft for more details, and we will update the story if we hear back.

 

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