Backdoor.MSIL.SUNBURST.A

This Backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It executes commands from a remote malicious user, effectively compromising the affected system.

Arrival Details

This Backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Backdoor Routine

This Backdoor executes the following commands from a remote malicious user:

• Delete Registry Value
• Get Registry Subkey and Value Names
• Read Registry Value
• Set Registry Value
• Delete File
• Check if File Exists
• Get File Hash
• Get File System Entries
• Write File
• Get Process By Description
• Kill Task
• Run Task
• Set Time - Set delay time
• Upload System Description
• Reboot -> Reboots computer
• Idle -> no operation
• Exit -> exits the thread
• Collect System description (Collects Domain Name, Hostname, Username, OS Version, Total Days since execution, System Directory location, Network Adapter Configuration where Network Adapter Configuration contains the following):
  • Description
  • Mac Address
  • DHCPEnabled
  • DHCPServer
  • DNSHostName
  • DNSDomainSuffixSearchOrder
  • IPAddress
  • DNSServerSearchOrder
  • IPSubnet
  • DefaultIPGateway

It connects to the following URL(s) to send and receive commands from a remote malicious user:

• {random characters}.appsync-api.{random string from list}.{BLOCKED}loud.com
• where {random string from list} can be any of the following:
  • eu-west-1
  • eu-west-2
  • us-east-1
  • us-east-2

Information Theft

This Backdoor gathers the following data:

• Used to generate UserId:
  • Domain Name
  • Network Interfaces
  • MachineGuid
• For checking blocklisted:
  • List of all running processes
  • List of drivers
  • List of services

Other Details

This Backdoor connects to the following URL(s) to check for an Internet connection:

• api.solarwinds.com

It does the following:

• Uses the following to regex to parse response body:
  • "\"\{[0-9a-f-]{36}\}\"|\"[0-9a-f]{32}\"|\"[0-9a-f]{16}\""
• Checks the joined domain of the machine for the following patterns: (will terminate if matched):
  • "(?i)([^a-z]|^)(test)([^a-z]|$)"
  • "(?i)(solarwinds)"
• Checks DGA URLs for the following blocks of IP Addresses, enumerate services found in the malware configuration, changes the start value of those services, and will not proceed to C2 connection if found:
  • 10.0.0.0/8
  • 172.16.0.0/12
  • 192.168.0.0/16
  • 224.0.0.0/3
  • fc00:: - fe00::
  • fec0:: - ffc0::
  • ff00:: - ff00::
  • 20.140.0.0/15
  • 96.31.172.0/24
  • 131.228.12.0/22
  • 144.86.226.0/24
• Checks for the following conditions before proceeding to the backdoor routine:
  • Process name hash should be 17291806236368054941 after hashing function (matches processname businesslayerhost.exe)
  • Installation date should be 12 days or more
  • Checks ReportWatcherRetry key in the config and if value is not 3 (Truncate)
  • Checks if machine is joined in a domain
• Creates the following named pipe to ensure one instance is only running:
  • 583da945-62af-10e8-4902-a8f205c72b2e
• Checks the DGA URLs for the following blocks of IP Addresses, and updates the status configuration of the malware:
  • 41.84.159.0/255.255.255.0
  • 71.114.24.0/255.255.248.0
  • 154.118.140.0/255.255.255.0
  • 217.163.7.0/255.255.255.0
• Checks DGA URLs for the following blocks of IP Addresses, and proceeds to backdoor routine if found:
  • 8.18.144.0/255.255.254.0
  • 18.130.0.0/255.255.0.0
  • 71.152.53.0/255.255.255.0
  • 99.79.0.0/255.255.0.0
  • 87.238.80.0/255.255.248.0
  • 199.201.117.0/255.255.255.0
  • 184.72.0.0/255.254.0.0