Suspicious Encoded And Obfuscated Reflection Assembly Load Function Call

Severity: high
Author: pH-T (Nextron Systems)
Source: upstream

Detects suspicious base64 encoded and obfuscated "LOAD" keyword used in .NET "reflection.assembly"

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1059.001` Command and Scripting Interpreter: PowerShell
Defense Evasion	`T1027` Obfuscated Files or Information

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation
Security-Auditing	4688	A new process has been created.

Stages and Predicates

Stage 1: `selection`

or:
CommandLine|contains: '6ADoAKAAiAEwAIgArACIAbwBhAGQAIgApA'
CommandLine|contains: '6ADoAKAAiAEwAbwAiACsAIgBhAGQAIgApA'
CommandLine|contains: '6ADoAKAAiAEwAbwBhACIAKwAiAGQAIgApA'
CommandLine|contains: '6ADoAKAAnAEwAJwArACcAbwBhAGQAJwApA'
CommandLine|contains: '6ADoAKAAnAEwAbwAnACsAJwBhAGQAJwApA'
CommandLine|contains: '6ADoAKAAnAEwAbwBhACcAKwAnAGQAJwApA'
CommandLine|contains: 'OgA6ACgAIgBMACIAKwAiAG8AYQBkACIAKQ'
CommandLine|contains: 'OgA6ACgAIgBMAG8AIgArACIAYQBkACIAKQ'
CommandLine|contains: 'OgA6ACgAIgBMAG8AYQAiACsAIgBkACIAKQ'
CommandLine|contains: 'OgA6ACgAJwBMACcAKwAnAG8AYQBkACcAKQ'
CommandLine|contains: 'OgA6ACgAJwBMAG8AJwArACcAYQBkACcAKQ'
CommandLine|contains: 'OgA6ACgAJwBMAG8AYQAnACsAJwBkACcAKQ'
CommandLine|contains: 'oAOgAoACIATAAiACsAIgBvAGEAZAAiACkA'
CommandLine|contains: 'oAOgAoACIATABvACIAKwAiAGEAZAAiACkA'
CommandLine|contains: 'oAOgAoACIATABvAGEAIgArACIAZAAiACkA'
CommandLine|contains: 'oAOgAoACcATAAnACsAJwBvAGEAZAAnACkA'
CommandLine|contains: 'oAOgAoACcATABvACcAKwAnAGEAZAAnACkA'
CommandLine|contains: 'oAOgAoACcATABvAGEAJwArACcAZAAnACkA'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.