Name:Detect Webshell Exploit Behavior id:22597426-6dbd-49bd-bcdc-4ec19857192f version:5 date:2024-11-28 author:Steven Dick status:production type:TTP Description:The following analytic identifies the execution of suspicious processes typically associated with webshell activity on web servers. It detects when processes like `cmd.exe`, `powershell.exe`, or `bash.exe` are spawned by web server processes such as `w3wp.exe` or `nginx.exe`. This behavior is significant as it may indicate an adversary exploiting a web application vulnerability to install a webshell, providing persistent access and command execution capabilities. If confirmed malicious, this activity could allow attackers to maintain control over the compromised server, execute arbitrary commands, and potentially escalate privileges or exfiltrate sensitive data. Data_source:
-Sysmon EventID 1
-Windows Event Log Security 4688
-CrowdStrike ProcessRollup2
search:| tstats `security_content_summariesonly` count max(_time) as lastTime, min(_time) as firstTime from datamodel=Endpoint.Processes where (Processes.process_name IN ("arp.exe","at.exe","bash.exe","bitsadmin.exe","certutil.exe","cmd.exe","cscript.exe", "dsget.exe","dsquery.exe","find.exe","findstr.exe","fsutil.exe","hostname.exe","ipconfig.exe","ksh.exe","nbstat.exe", "net.exe","net1.exe","netdom.exe","netsh.exe","netstat.exe","nltest.exe","nslookup.exe","ntdsutil.exe","pathping.exe", "ping.exe","powershell.exe","pwsh.exe","qprocess.exe","query.exe","qwinsta.exe","reg.exe","rundll32.exe","sc.exe", "scrcons.exe","schtasks.exe","sh.exe","systeminfo.exe","tasklist.exe","tracert.exe","ver.exe","vssadmin.exe", "wevtutil.exe","whoami.exe","wmic.exe","wscript.exe","wusa.exe","zsh.exe") AND Processes.parent_process_name IN ("w3wp.exe", "http*.exe", "nginx*.exe", "php*.exe", "php-cgi*.exe","tomcat*.exe")) by Processes.dest,Processes.user,Processes.parent_process,Processes.parent_process_name,Processes.process,Processes.process_name | `drop_dm_object_name("Processes")` | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `detect_webshell_exploit_behavior_filter`
how_to_implement:The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint` data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process. known_false_positives:Legitimate OS functions called by vendor applications, baseline the environment and filter before enabling. Recommend throttle by dest/process_name References: -https://attack.mitre.org/techniques/T1505/003/ -https://github.com/nsacyber/Mitigating-Web-Shells -https://www.hackingarticles.in/multiple-ways-to-exploit-tomcat-manager/ drilldown_searches: name:'View the detection results for - "$user$" and "$dest$"' search:'%original_detection_search% | search user = "$user$" dest = "$dest$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$user$" and "$dest$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$", "$dest$") starthoursago=168 | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' tags: analytic_story: - 'ProxyNotShell' - 'CISA AA22-257A' - 'HAFNIUM Group' - 'Citrix ShareFile RCE CVE-2023-24489' - 'ProxyShell' - 'Flax Typhoon' - 'CISA AA22-264A' - 'SysAid On-Prem Software CVE-2023-47246 Vulnerability' - 'Compromised Windows Host' - 'WS FTP Server Critical Vulnerabilities' - 'BlackByte Ransomware' asset_type:Endpoint confidence:80 impact:100 message:Webshell Exploit Behavior - $parent_process_name$ spawned $process_name$ on $dest$. mitre_attack_id: - 'T1505' - 'T1505.003' observable: name:'user' type:'User' - role: - 'Victim' name:'dest' type:'Endpoint' - role: - 'Victim' name:'process_name' type:'Process' - role: - 'Attacker' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - '_time' - 'Processes.dest' - 'Processes.user' - 'Processes.parent_process' - 'Processes.parent_process_name' - 'Processes.process' - 'Processes.process_name' risk_score:80 security_domain:endpoint supported_tas: - 'Splunk_TA_microsoft_sysmon'
