Techniques
Sample rules
MS Exchange Mailbox Replication service writing Active Server Pages
- source: splunk
- technicques:
- T1133
- T1190
- T1505.003
Description
The following analytic identifies the creation of suspicious .aspx files in specific directories associated with Exchange exploitation by the HAFNIUM group and the ProxyShell vulnerability. It detects this activity by monitoring the MSExchangeMailboxReplication.exe process, which typically does not write .aspx files. This behavior is significant as it may indicate an active exploitation attempt on Exchange servers. If confirmed malicious, attackers could gain unauthorized access, execute arbitrary code, or maintain persistence within the environment. Immediate investigation and remediation are crucial to prevent further compromise.
Detection logic
| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes where Processes.process_name=MSExchangeMailboxReplication.exe by _time span=1h Processes.process_id Processes.process_name Processes.process_guid Processes.dest
| `drop_dm_object_name(Processes)`
| join process_guid, _time [
| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem where Filesystem.file_path IN ("*\\HttpProxy\\owa\\auth\\*", "*\\inetpub\\wwwroot\\aspnet_client\\*", "*\\HttpProxy\\OAB\\*") Filesystem.file_name="*.aspx" by _time span=1h Filesystem.dest Filesystem.file_create_time Filesystem.file_name Filesystem.file_path
| `drop_dm_object_name(Filesystem)`
| fields _time dest file_create_time file_name file_path process_name process_path process process_guid]
| dedup file_create_time
| table dest file_create_time, file_name, file_path, process_name
| `ms_exchange_mailbox_replication_service_writing_active_server_pages_filter`
Detect Exchange Web Shell
- source: splunk
- technicques:
- T1133
- T1190
- T1505.003
Description
The following analytic identifies the creation of suspicious .aspx files in known drop locations for Exchange exploitation, specifically targeting paths associated with HAFNIUM group and vulnerabilities like ProxyShell and ProxyNotShell. It leverages data from the Endpoint datamodel, focusing on process and filesystem events. This activity is significant as it may indicate a web shell deployment, a common method for persistent access and remote code execution. If confirmed malicious, attackers could gain unauthorized access, execute arbitrary commands, and potentially escalate privileges within the Exchange environment.
Detection logic
| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes where Processes.process_name=System by _time span=1h Processes.process_guid Processes.process_name Processes.process Processes.dest Processes.user
| `drop_dm_object_name(Processes)`
| join process_guid, _time [
| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem where Filesystem.file_path IN ("*\\HttpProxy\\owa\\auth\\*", "*\\inetpub\\wwwroot\\aspnet_client\\*", "*\\HttpProxy\\OAB\\*") Filesystem.file_name IN( "*.aspx", "*.ashx") by _time span=1h Filesystem.process_guid Filesystem.user Filesystem.dest Filesystem.file_create_time Filesystem.file_name Filesystem.file_path
| `drop_dm_object_name(Filesystem)` ]
| dedup file_create_time
| table _time dest user file_create_time file_name file_path process_name process process_guid
| `detect_exchange_web_shell_filter`
Windows Office Product Dropped Cab or Inf File
- source: splunk
- technicques:
- T1566.001
Description
The following analytic detects Office products writing .cab or .inf files, indicative of CVE-2021-40444 exploitation. It leverages the Endpoint.Processes and Endpoint.Filesystem data models to identify Office applications creating these file types. This activity is significant as it may signal an attempt to load malicious ActiveX controls and download remote payloads, a known attack vector. If confirmed malicious, this could lead to remote code execution, allowing attackers to gain control over the affected system and potentially compromise sensitive data.
Detection logic
| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes where `process_office_products` by _time span=1h Processes.process_id Processes.process_name Processes.process Processes.dest Processes.process_guid
| `drop_dm_object_name(Processes)`
|rename process_guid as proc_guid
| join proc_guid, _time [
| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem where Filesystem.file_name IN ("*.cab", "*.inf") by _time span=1h Filesystem.dest Filesystem.file_create_time Filesystem.file_name Filesystem.file_path Filesystem.process_guid
| `drop_dm_object_name(Filesystem)`
|rename process_guid as proc_guid
| fields _time dest file_create_time file_name file_path process_name process_path process proc_guid]
| dedup file_create_time
| table dest, process_name, process, file_create_time, file_name, file_path, proc_guid
| `windows_office_product_dropped_cab_or_inf_file_filter`
Windows MOVEit Transfer Writing ASPX
- source: splunk
- technicques:
- T1190
- T1133
Description
The following analytic detects the creation of new ASPX files in the MOVEit Transfer application’s “wwwroot” directory. It leverages endpoint data on process and filesystem activity to identify processes responsible for creating these files. This activity is significant as it may indicate exploitation of a critical zero-day vulnerability in MOVEit Transfer, used by threat actors to install malicious ASPX files. If confirmed malicious, this could lead to exfiltration of sensitive data, including user credentials and file metadata, posing a severe risk to the organization’s security.
Detection logic
| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes where Processes.process_name=System by _time span=1h Processes.process_id Processes.process_name Processes.dest
| `drop_dm_object_name(Processes)`
| join process_guid, _time [
| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem where Filesystem.file_path IN ("*\\MOVEitTransfer\\wwwroot\\*") Filesystem.file_name IN("*.aspx", "*.ashx", "*.asp*") OR Filesystem.file_name IN ("human2.aspx","_human2.aspx") by _time span=1h Filesystem.dest Filesystem.file_create_time Filesystem.file_name Filesystem.file_path
| `drop_dm_object_name(Filesystem)`
| fields _time dest file_create_time file_name file_path process_name process_path process]
| dedup file_create_time
| table dest file_create_time, file_name, file_path, process_name
| `windows_moveit_transfer_writing_aspx_filter`