YARA Detection Rule: APT_Backdoor_SUNBURST_1
Repository: Neo23x0/signature-base
Detects: This rule is looking for portions of the SUNBURST backdoor that are vital to how it functions. The first signature fnv_xor matches a magic byte xor that the sample performs on process, service, and driver names/paths. SUNBURST is a backdoor that has the ability to spawn and kill processes, write and delete files, set and create registry keys, gather system information, and disable a set of forensic analysis tools and services.
Author: FireEye
Reference: https://www.fireeye.com/blog/threat-research/2020/12/evasive-attacker-leverages-solarwinds-supply-chain-compromises-with-sunburst-backdoor.html

Pattern signatures:
$cmd_regex_encoded = "U4qpjjbQtUzUTdONrTY2q42pVapRgooABYxQuIZmtUoA" wide
        $cmd_regex_plain = { 5C 7B 5B 30 2D 39 61 2D 66 2D 5D 7B 33 36 7D 5C 7D 22 7C 22 5B 30 2D 39 61 2D 66 5D 7B 33 32 7D 22 7C 22 5B 30 2D 39 61 2D 66 5D 7B 31 36 7D }
        $fake_orion_event_encoded = "U3ItS80rCaksSFWyUvIvyszPU9IBAA==" wide
        $fake_orion_event_plain = { 22 45 76 65 6E 74 54 79 70 65 22 3A 22 4F 72 69 6F 6E 22 2C }
        $fake_orion_eventmanager_encoded = "U3ItS80r8UvMTVWyUgKzfRPzEtNTi5R0AA==" wide
        $fake_orion_eventmanager_plain = { 22 45 76 65 6E 74 4E 61 6D 65 22 3A 22 45 76 65 6E 74 4D 61 6E 61 67 65 72 22 2C }
        $fake_orion_message_encoded = "U/JNLS5OTE9VslKqNqhVAgA=" wide
        $fake_orion_message_plain = { 22 4D 65 73 73 61 67 65 22 3A 22 7B 30 7D 22 }
        $fnv_xor = { 67 19 D8 A7 3B 90 AC 5B }

Detection condition:
$fnv_xor and ($cmd_regex_encoded or $cmd_regex_plain) or ( ($fake_orion_event_encoded or $fake_orion_event_plain) and ($fake_orion_eventmanager_encoded or $fake_orion_eventmanager_plain) and ($fake_orion_message_encoded and $fake_orion_message_plain) )

Full rule:
rule APT_Backdoor_SUNBURST_1
{
    meta:
        author = "FireEye"
        description = "This rule is looking for portions of the SUNBURST backdoor that are vital to how it functions. The first signature fnv_xor matches a magic byte xor that the sample performs on process, service, and driver names/paths. SUNBURST is a backdoor that has the ability to spawn and kill processes, write and delete files, set and create registry keys, gather system information, and disable a set of forensic analysis tools and services."
        reference = "https://www.fireeye.com/blog/threat-research/2020/12/evasive-attacker-leverages-solarwinds-supply-chain-compromises-with-sunburst-backdoor.html"
        date = "2020-12-14"
        score = 85
        id = "74b44844-5575-53d7-819b-ab1b2327a144"
    strings:
        $cmd_regex_encoded = "U4qpjjbQtUzUTdONrTY2q42pVapRgooABYxQuIZmtUoA" wide
        $cmd_regex_plain = { 5C 7B 5B 30 2D 39 61 2D 66 2D 5D 7B 33 36 7D 5C 7D 22 7C 22 5B 30 2D 39 61 2D 66 5D 7B 33 32 7D 22 7C 22 5B 30 2D 39 61 2D 66 5D 7B 31 36 7D }
        $fake_orion_event_encoded = "U3ItS80rCaksSFWyUvIvyszPU9IBAA==" wide
        $fake_orion_event_plain = { 22 45 76 65 6E 74 54 79 70 65 22 3A 22 4F 72 69 6F 6E 22 2C }
        $fake_orion_eventmanager_encoded = "U3ItS80r8UvMTVWyUgKzfRPzEtNTi5R0AA==" wide
        $fake_orion_eventmanager_plain = { 22 45 76 65 6E 74 4E 61 6D 65 22 3A 22 45 76 65 6E 74 4D 61 6E 61 67 65 72 22 2C }
        $fake_orion_message_encoded = "U/JNLS5OTE9VslKqNqhVAgA=" wide
        $fake_orion_message_plain = { 22 4D 65 73 73 61 67 65 22 3A 22 7B 30 7D 22 }
        $fnv_xor = { 67 19 D8 A7 3B 90 AC 5B }
    condition:
        $fnv_xor and ($cmd_regex_encoded or $cmd_regex_plain) or ( ($fake_orion_event_encoded or $fake_orion_event_plain) and ($fake_orion_eventmanager_encoded or $fake_orion_eventmanager_plain) and ($fake_orion_message_encoded and $fake_orion_message_plain) )
}