PowerShellEncodedReconActivities.md

Encoded Powershell Commands That Have Potentially Performed Recon Activities

Query Information

MITRE ATT&CK Technique(s)

Technique ID	Title	Link
T1027	Obfuscated Files or Information	https://attack.mitre.org/techniques/T1027/
T1087.004	Account Discovery: Cloud Account	https://attack.mitre.org/techniques/T1087/004/

Description

PowerShell can be used send discovery requests, for example listing AD users or Groups. This can also be done with encoded powershell commands to evade detection. This query lists all encoded powershell executions that possible discovery activities.

Risk

An advasary uses an encoded PowerShell command to collect information on of other systems or Active Directory.

References

• https://unit42.paloaltonetworks.com/unit42-pulling-back-the-curtains-on-encodedcommand-powershell-attacks/
• https://community.sophos.com/sophos-labs/b/blog/posts/decoding-malicious-powershell
• https://www.trendmicro.com/vinfo/us/security/news/cybercrime-and-digital-threats/tracking-detecting-and-thwarting-powershell-based-malware-and-attacks

Defender XDR

let EncodedList = dynamic(['-encodedcommand', '-enc']); 
// For more results use line below en filter one above. This will also return more FPs.
// let EncodedList = dynamic(['-encodedcommand', '-enc', '-e']);
let ReconVariables = dynamic(['Get-ADGroupMember', 'Get-ADComputer', 'Get-ADUser', 'Get-NetGPOGroup', 'net user', 'whoami', 'net group', 'hostname', 'netsh firewall', 'tasklist', 'arp', 'systeminfo']);
let TimeFrame = 48h; //Customizable h = hours, d = days
DeviceProcessEvents
| where Timestamp > ago(TimeFrame)
| where ProcessCommandLine contains "powershell" or InitiatingProcessCommandLine contains "powershell"
| where ProcessCommandLine has_any (EncodedList) or InitiatingProcessCommandLine has_any (EncodedList)
| extend base64String = extract(@'\s+([A-Za-z0-9+/]{20}\S+$)', 1, ProcessCommandLine)
| extend DecodedCommandLine = base64_decode_tostring(base64String)
| extend DecodedCommandLineReplaceEmptyPlaces = replace_string(DecodedCommandLine, '\u0000', '')
| where isnotempty(base64String) and isnotempty(DecodedCommandLineReplaceEmptyPlaces)
// Search in the decoded commandline for Recon variables
| where DecodedCommandLineReplaceEmptyPlaces has_any (ReconVariables)
| project-reorder 
     Timestamp,
     ActionType,
     DecodedCommandLineReplaceEmptyPlaces,
     ProcessCommandLine,
     InitiatingProcessCommandLine,
     DeviceName,
     AccountName,
     AccountDomain

Sentinel

let EncodedList = dynamic(['-encodedcommand', '-enc']); 
// For more results use line below en filter one above. This will also return more FPs.
// let EncodedList = dynamic(['-encodedcommand', '-enc', '-e']);
let ReconVariables = dynamic(['Get-ADGroupMember', 'Get-ADComputer', 'Get-ADUser', 'Get-NetGPOGroup', 'net user', 'whoami', 'net group', 'hostname', 'netsh firewall', 'tasklist', 'arp', 'systeminfo']);
let TimeFrame = 48h; //Customizable h = hours, d = days
DeviceProcessEvents
| where TimeGenerated > ago(TimeFrame)
| where ProcessCommandLine contains "powershell" or InitiatingProcessCommandLine contains "powershell"
| where ProcessCommandLine has_any (EncodedList) or InitiatingProcessCommandLine has_any (EncodedList)
| extend base64String = extract(@'\s+([A-Za-z0-9+/]{20}\S+$)', 1, ProcessCommandLine)
| extend DecodedCommandLine = base64_decode_tostring(base64String)
| extend DecodedCommandLineReplaceEmptyPlaces = replace_string(DecodedCommandLine, '\u0000', '')
| where isnotempty(base64String) and isnotempty(DecodedCommandLineReplaceEmptyPlaces)
// Search in the decoded commandline for Recon variables
| where DecodedCommandLineReplaceEmptyPlaces has_any (ReconVariables)
| project
     TimeGenerated,
     ActionType,
     DecodedCommandLineReplaceEmptyPlaces,
     ProcessCommandLine,
     InitiatingProcessCommandLine,
     DeviceName,
     AccountName,
     AccountDomain