Analytics Story: ProxyNotShell

Date: 2022-09-30 ID: 4e3f17e7-9ed7-425d-a05e-b65464945836 Author: Michael Haag, Splunk Product: Splunk Enterprise Security

Description

Two new zero day Microsoft Exchange vulnerabilities have been identified actively exploited in the wild - CVE-2022-41040 and CVE-2022-41082.

Why it matters

Microsoft is investigating two reported zero-day vulnerabilities affecting Microsoft Exchange Server 2013, 2016, and 2019. The first vulnerability, identified as CVE-2022-41040, is a Server-Side Request Forgery (SSRF) vulnerability, while the second, identified as CVE-2022-41082, allows remote code execution (RCE) when PowerShell is accessible to the attacker. Originally identified by GTSC monitoring Exchange, some adversary post-exploitation activity was identified and is tagged to this story.

Correlation Search

1| tstats `security_content_summariesonly` min(_time) as firstTime max(_time) as lastTime sum(All_Risk.calculated_risk_score) as risk_score, count(All_Risk.calculated_risk_score) as risk_event_count, values(All_Risk.annotations.mitre_attack.mitre_tactic_id) as annotations.mitre_attack.mitre_tactic_id, dc(All_Risk.annotations.mitre_attack.mitre_tactic_id) as mitre_tactic_id_count, values(All_Risk.analyticstories) as analyticstories values(All_Risk.annotations.mitre_attack.mitre_technique_id) as annotations.mitre_attack.mitre_technique_id, dc(All_Risk.annotations.mitre_attack.mitre_technique_id) as mitre_technique_id_count, values(All_Risk.tag) as tag, values(source) as source, dc(source) as source_count dc(All_Risk.analyticstories) as dc_analyticstories from datamodel=Risk.All_Risk where All_Risk.analyticstories IN ("ProxyNotShell","ProxyShell") OR (All_Risk.analyticstories IN ("ProxyNotShell","ProxyShell") AND All_Risk.analyticstories="Cobalt Strike") All_Risk.risk_object_type="system" by _time span=1h All_Risk.risk_object All_Risk.risk_object_type | `drop_dm_object_name(All_Risk)` | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`| where source_count >=5 | `proxyshell_proxynotshell_behavior_detected_filter`

Detections

Name ▲▼	Technique ▲▼	Type ▲▼
CMD Carry Out String Command Parameter	Windows Command Shell	Hunting
Detect Exchange Web Shell	External Remote Services, Exploit Public-Facing Application, Web Shell	TTP
Exchange PowerShell Abuse via SSRF	Exploit Public-Facing Application, External Remote Services	TTP
Exchange PowerShell Module Usage	PowerShell	TTP
W3WP Spawning Shell	Web Shell	TTP
Windows File Download Via CertUtil	Ingress Tool Transfer	TTP
Windows MSExchange Management Mailbox Cmdlet Usage	PowerShell	Anomaly
Windows Suspicious Child Process Spawned From WebServer	Web Shell	TTP
Windows Exchange Autodiscover SSRF Abuse	Exploit Public-Facing Application, External Remote Services	TTP

Data Sources

Name ▲▼	Platform ▲▼	Sourcetype ▲▼	Source ▲▼
Cisco Network Visibility Module Flow Data	Network	`cisco:nvm:flowdata`	`not_applicable`
CrowdStrike ProcessRollup2	N/A	`crowdstrike:events:sensor`	`crowdstrike`
Powershell Script Block Logging 4104	Windows	`xmlwineventlog`	`XmlWinEventLog:Microsoft-Windows-PowerShell/Operational`
Sysmon EventID 1	Windows	`xmlwineventlog`	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`
Sysmon EventID 11	Windows	`xmlwineventlog`	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`
Windows Event Log Security 4688	Windows	`xmlwineventlog`	`XmlWinEventLog:Security`
Windows IIS	Windows	`IIS:Configuration:Operational`	`IIS:Configuration:Operational`

References

Source: GitHub | Version: 1