What Is ShrinkLocker? New Ransomware Targets Microsoft BitLocker Encryption Characteristic


A brand new pressure of ransomware dubbed ShrinkLocker is being utilized by cyberattackers to focus on enterprise computer systems. It exploits the Microsoft BitLocker encryption function to encrypt the whole native drive and take away the restoration choices earlier than shutting down the PC. ShrinkLocker was found by cybersecurity agency Kaspersky, and analysts have noticed variants in Mexico, Indonesia and Jordan.

BitLocker has been used to stage ransomware assaults up to now, however this pressure has “beforehand unreported options to maximise the injury of the assault,” Kaspersky said in a press release. ShrinkLocker is exclusive in that it may verify the model of a tool’s Home windows working system to make sure it allows the suitable BitLocker options, however deletes itself if it may’t.

Cristian Souza, incident response specialist at Kaspersky International Emergency Response Crew, stated within the press launch, “What is especially regarding about this case is that BitLocker, initially designed to mitigate the dangers of knowledge theft or publicity, has been repurposed by adversaries for malicious ends. It’s a merciless irony {that a} safety measure has been weaponized on this method.”

Who’s susceptible to ShrinkLocker assault?

Firms in metal and vaccine manufacturing, in addition to a authorities entity, have been focused with ShrinkLocker to this point. Nevertheless, Souza instructed TechRepublic there “is not any proof to imagine that this group is concentrating on particular industries,” as victims are from completely different international locations and sectors.

BitLocker is at present solely obtainable on the Professional, Enterprise, Schooling and Final editions of Home windows working methods, however it is going to be included and robotically activated in all variations with the discharge of Home windows 11 24H2 later this yr. This considerably will increase the potential scope of ShrinkLocker victims.

“Infections by ShrinkLocker will be crucial if the sufferer doesn’t have satisfactory proactive and reactive measures in place,” Souza added. “Since BitLocker is a local Home windows function, any machine with Home windows Vista+ or Server 2008+ may very well be affected.”

How does ShrinkLocker work?

Though ShrinkLocker self-deletes after encrypting the goal, Kaspersky analysts had been capable of uncover the way it works by finding out a script left behind on a drive on a PC that was contaminated however didn’t have BitLocker configured.

Attackers would possibly deploy ShrinkLocker on a tool by exploiting unpatched vulnerabilities, stolen credentials or internet-facing providers to realize entry to servers. A person can also unintentionally obtain the script, for instance, by a hyperlink in a phishing e-mail.

“As soon as they’ve entry to the goal system, the attacker can attempt to exfiltrate info and eventually execute the ransomware to encrypt the information,” Souza instructed TechRepublic.

As soon as the script is triggered, it makes use of Home windows Administration Instrumentation extensions and the Win32_OperatingSystem class to question details about the system’s working system and area. If the system runs on Home windows XP, 2000, 2003 or Vista, or the present area of the queried objects doesn’t match the goal, the script deletes itself.

SEE: Is there a simple way to recover encrypted BitLocker drives?

Nevertheless, if the PC is utilizing Home windows 2008 or earlier, the script will transfer on to resizing its native fastened drives. It shrinks non-boot partitions by 100MB to create unallocated disk area, which is why it has been dubbed ShrinkLocker. New major partitions are created within the unallocated area, and the boot recordsdata are reinstalled so the system will be rebooted with the encrypted recordsdata by the sufferer.

Disk resizing operations performed by the script in Windows Server 2008 and 2012.
Disk resizing operations carried out by the script in Home windows Server 2008 and 2012. Picture: Kaspersky

Subsequent, the script modifies Home windows registry entries to disable Distant Desktop Protocol connections and implement BitLocker settings like PIN necessities. It then renames the boot partitions with the attacker’s e-mail — onboardingbinder[at]proton[dot]me or conspiracyid9[at]protonmail[dot]com — and replaces current BitLocker key protectors to forestall restoration.

ShrinkLocker creates a brand new 64-character encryption key utilizing the random multiplication and alternative of the next parts:

  • A variable with the numbers zero to 9.
  • The pangram “The fast brown fox jumps over the lazy canine,” which accommodates each letter of the English alphabet, in lowercase and uppercase.
  • Particular characters.

It then allows BitLocker encryption on all the system’s drives. ShrinkLocker solely encrypts the native, fastened drive of the contaminated PC and doesn’t infect community drives seemingly to assist evade detection.

The 64-character key and a few system info are despatched to the attacker’s server through an HTTP POST request to a randomly generated subdomain of ‘trycloudflare[dot]com.’ It is a reputable area from CloudFlare that’s meant for use by builders for testing out CloudFlare Tunnel with out including a web site to CloudFlare’s DNS. The attackers exploit it right here to cover their actual tackle.

Lastly, ShrinkLocker self-deletes its script and scheduled duties, clears the logs, activates the firewall and deletes all the foundations earlier than forcing a shutdown. When the person reboots the system, they’re offered with the BitLocker restoration display screen with no restoration choices obtainable — all of the PC’s knowledge is encrypted, locked and out of attain.

When the user reboots a device infected with ShrinkLocker, they are presented with the BitLocker recovery screen with no recovery options available.
When the person reboots a tool contaminated with ShrinkLocker, they’re offered with the BitLocker restoration display screen with no restoration choices obtainable. Picture: Kaspersky

The brand new drive labels with the attacker’s e-mail instruct the person to contact them, implying a ransom demand for the decryption key.

Attacker’s email as a drive label.
Attacker’s e-mail as a drive label. Picture: Kaspersky

In a technical analysis, Kaspersky analysts describe each the detection of a ShrinkLocker assault and the decryption course of as “tough.” The latter is especially exhausting as a result of the malicious script accommodates variables which might be completely different for every affected system.

Who’s liable for the ShrinkLocker assaults?

Kaspersky specialists have, to this point, not been capable of determine the supply of the ShrinkLocker assaults or the place the decryption keys and different system info are despatched. Nevertheless, some details about the attackers will be gleaned from the malware script.

The analysts stated that the script, written in VBScript, “demonstrates that the malicious actor(s) concerned on this assault have a wonderful understanding of Home windows internals.”

The labels containing the attacker’s e-mail tackle can solely be considered if the contaminated system is booted by an admin in a restoration atmosphere or with diagnostic instruments, in accordance with BleepingComputer. Moreover, the BitLocker restoration display screen can have a customized observe added, but the attackers particularly selected to not create one.

The truth that the attackers seem to have deliberately made it tough to contact them suggests their motives are disruption and destruction reasonably than monetary achieve.

“For now, we all know we’re coping with a really expert group,” Souza instructed TechRepublic. “The malware we had been capable of analyse exhibits that the attackers have a deep understanding of the working system’s internals and numerous living-off-the-land instruments.”

How can companies defend themselves towards ShrinkLocker?

Kaspersky supplies the next recommendation to companies seeking to defend their units from the ShrinkLocker an infection:

  • Use sturdy, correctly configured endpoint safety platforms to detect potential malicious exercise earlier than encryption.
  • Implement managed detection and response to proactively scan for threats.
  • Guarantee BitLocker has a robust password and the restoration keys are saved in a safe location.
  • Restrict person privileges to the minimal required to do their job. This manner, no unauthorised personnel can allow encryption options or change registry keys on their very own.
  • Allow community site visitors logging and monitoring, capturing each GET and POST requests, as contaminated methods could transmit passwords or keys to attacker domains.
  • Monitor for VBScript and PowerShell execution occasions, saving logged scripts and instructions to an exterior repository to retain exercise even when native information are deleted.
  • Make backups continuously, retailer them offline and check them.

How has BitLocker been focused up to now?

BitLocker has been focused by dangerous actors quite a few instances up to now, nicely earlier than the emergence of ShrinkLocker. In 2021, a hospital in Belgium had 40 servers and 100 TB of its knowledge encrypted after an attacker exploited BitLocker, resulting in delays in surgical procedures and the redirection of sufferers to different services.

The next yr, one other attacker focused one of Russia’s largest meat suppliers in the identical method, earlier than Microsoft reported the Iranian government had sponsored a number of BitLocker-based ransomware attacks that demanded hundreds of U.S. {dollars} for the decryption key.



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