Threat Signal Report

Meet BlackByte Ransomware

description-logo Description

FortiGuard Labs is aware of a relatively new ransomware family "BlackByte" is in the wild, infecting organizations around the globe. BlackByte was first observed as early as July 2021. In February 2022, the Federal Bureau of Investigation (FBI) and the U.S. Secret Service (USSS) issued a joint advisory that "multiple US and foreign businesses, including entities in at least three US critical infrastructure sectors (government facilities, financial, and food & agriculture) were targeted by BlackByte ransomware affiliates. In common with other ransomware, BlackByte encrypts and steals files on the compromised machines, and demands ransom from the victim to recover the files and not to leak the stolen information to the public.

Why is this Significant?

This is significant as the BlackByte ransomware family reportedly compromised organizations around the globe including multiple US and foreign businesses and US critical infrastructure sectors. Also, ProxyShell, an exploit attack chain involving three vulnerabilities in Microsoft Exchange Server, widely used in enterprise email application, were reported to have been used as an infection vector. Microsoft issued patches for ProxyShell in May and July 2021. BlackByte ransomware infection may indicate that some organizations have not yet applied those fixes or workaround.

FortiGuard Labs previously published multiple Threat Signals on ProxyShell. See the Appendix section for links to

  • New Threat Actor Leverages ProxyShell Exploit to Serve Ransomware
  • Vulnerable Microsoft Exchange Servers Actively Scanned for ProxyShell
  • Brand New LockFile Ransomware Distributed Through ProxyShell and PetitPotam

What is BlackByte?

BlackByte is a ransomware-as-a-service (RaaS), which runs a business of leasing necessary ransomware services to its affiliates. Such ransomware services including developing ransomware, creating and maintaining necessary infrastructures (i.e., ransom payment portal), ransom negotiation with victims as well as provides support service to the affiliates. Attacks are typically carried out by BlackByte affiliates, who rent and use those services. Once a victim is compromised and ransom is paid, BlackByte developers take a portion of the ransom as a service fee.

How does the Attack Work?

Typically attacks that deliver ransomware arrive in emails, however the join advisory reported that BlackByte threat actors, in some case, exploited known Microsoft Exchange Server vulnerabilities including ProxyShell to gain access to the victim's network. Once the attacker gains a foothold in the victim's network, the attacker deploys tools such as oft-abused Cobalt Strike to move laterally across the network and escalate privileges before exfiltrating and encrypting files. Some BlackByte ransomware variants may have worm functionality, which allows itself to self-propagate through the victim's network.

Files that are encrypted by BlackByte ransomware typically have a ".blackbyte" file extension.

BlackByte ransomware reportedly avoids encrypting files if the ransomware detects compromised systems that use Russian and ex-USSR languages.

What is ProxyShell?

ProxyShell is a name for a Microsoft Exchange Server exploit chain (CVE-2021-34473, CVE-2021-34523 and CVE-2021-31207) that allows an attacker to bypass ACL controls, elevate privileges and execute remote code on the compromised system.

What is the Status of Coverage?

FortiGuard Labs provides the following AV coverage against currently available Indicator-of-Compromises (IOCs) associated with BlackByte ransomware:

  • RTF/BlackByte.DC56!tr.ransom
  • W64/BlackByte.DC56!tr.ransom
  • W32/Agent.CH!tr
  • W32/CobaltStrike.NV!tr
  • JS/Agent.49CC!tr
  • W32/PossibleThreat

FortiGuard Labs provides the following IPS coverage against three vulnerabilities that are leveraged in ProxyShell:

  • MS.Exchange.Server.CVE-2021-34473.Remote.Code.Execution (CVE-2021-34473)
  • MS.Exchange.Server.Common.Access.Token.Privilege.Elevation (CVE-2021-34523)
  • MS.Exchange.MailboxExportRequest.Arbitrary.File.Write (CVE-2021-31207)

FortiEDR detects and blocks ProxyShell attacks out of the box without any prior knowledge or special configuration beforehand.

Any Other Suggested Mitigation?

Due to the ease of disruption and potential for damage to daily operations, reputation, and unwanted release of personally identifiable information (PII), etc., it is important to keep all AV and IPS signatures up to date. It is also important to ensure that all known vendor vulnerabilities within an organization are addressed and updated to protect against attackers establishing a foothold within a network.

Also - organizations are encouraged to conduct ongoing training sessions to educate and inform personnel about the latest phishing/spearphishing attacks. They also need to encourage employees to never open attachments from someone they don't know, and to always treat emails from unrecognized/untrusted senders with caution. Since it has been reported that various phishing and spearphishing attacks have been delivered via social engineering distribution mechanisms, it is crucial that end users within an organization be made aware of the various types of attacks being delivered. This can be accomplished through regular training sessions and impromptu tests using predetermined templates by an organizations' internal security department. Simple user awareness training on how to spot emails with malicious attachments or links could also help prevent initial access into the network.

Disconnect vulnerable Exchange servers from the internet until a patch can be applied.


Traffic Light Protocol

Color When Should it Be used? How may it be shared?


Not for disclosure, restricted to participants only.
Sources may use TLP:RED when information cannot be effectively acted upon by additional parties, and could lead to impacts on a party's privacy, reputation, or operations if misused. Recipients may not share TLP:RED information with any parties outside of the specific exchange, meeting, or conversation in which it was originally disclosed. In the context of a meeting, for example, TLP:RED information is limited to those present at the meeting. In most circumstances, TLP:RED should be exchanged verbally or in person.


Limited disclosure, restricted to participants’ organizations.
Sources may use TLP:AMBER when information requires support to be effectively acted upon, yet carries risks to privacy, reputation, or operations if shared outside of the organizations involved. Recipients may only share TLP:AMBER information with members of their own organization, and with clients or customers who need to know the information to protect themselves or prevent further harm. Sources are at liberty to specify additional intended limits of the sharing: these must be adhered to.


Limited disclosure, restricted to the community.
Sources may use TLP:GREEN when information is useful for the awareness of all participating organizations as well as with peers within the broader community or sector. Recipients may share TLP:GREEN information with peers and partner organizations within their sector or community, but not via publicly accessible channels. Information in this category can be circulated widely within a particular community. TLP:GREEN information may not be released outside of the community.


Disclosure is not limited.
Sources may use TLP:WHITE when information carries minimal or no foreseeable risk of misuse, in accordance with applicable rules and procedures for public release. Subject to standard copyright rules, TLP:WHITE information may be distributed without restriction.