External Remote Services T1133
Adversaries may leverage external-facing remote services to initially access and/or persist within a network. Remote services such as VPNs, Citrix, and other access mechanisms allow users to connect to internal enterprise network resources from external locations. There are often remote service gateways that manage connections and credential authentication for these services. Services such as Windows Remote Management and VNC can also be used externally.
Events covered
17 catalog events are tagged with this technique by at least one rule.
Authoring guide
Patterns shared across the 28 rules above: which fields they filter on, what specific values they look for, and what they exclude. The catalog normalizes field names across vendors so Sigma's Image, Elastic's process.name, and Splunk's process_name collapse into one row. Each rule contributes at most once per row.
Fields filtered most (25 distinct)
The fields most rules look at when detecting this technique. The How column shows the operators authors use (eq, wildcard, regex_match, match) and how often each appears. Sample values are concrete examples to start from, not an exhaustive list.
Top indicator values (283 distinct)
Specific (field, operator, value) combinations the rules check for, ranked by how many rules under this technique use each one. The Corpus reach column counts how many rules across the entire catalog (any technique) check the same combination. High numbers point to widely-used indicators that are likely noisy on their own; combine them with another condition for useful signal. Blank means the combination is specific to rules under this technique. Click a value to expand the rules under this technique that use it.
Exclusions (12 distinct)
Field/operator/value combinations excluded by rules under this technique (top-level not() clauses), sorted by how many rules exclude each. These are the false-positive paths the community has learned to filter out. A new rule that ignores the high-count entries here will likely fire on the same noisy paths. Click a value to expand the rules under this technique that exclude it.
Rules under this technique
Every rule in the catalog tagged with this technique, grouped by vendor. Click a rule title for its full predicates, exclusions, and indicators.
Sigma 12 rules
- External Remote RDP Logon from Public IP
- External Remote SMB Logon from Public IP
- Failed Logon From Public IP
- Potential Exploitation of GoAnywhere MFT Vulnerability
- Remote Access Tool - ScreenConnect Installation Execution
- Remote Access Tool - Team Viewer Session Started On Windows Host
- Running Chrome VPN Extensions via the Registry 2 VPN Extension
- Suspicious File Created by ArcSOC.exe
- Unusual Child Process of dns.exe
- Unusual File Deletion by Dns.exe
- Unusual File Modification by dns.exe
- User Added to Remote Desktop Users Group
Splunk 16 rules
- Detect Exchange Web Shell
- Disabled Pre-Authentication Accounts Discovery - PowerShell (PowerShell)
- Disabled Pre-Authentication Accounts Discovery - PowerShell (Sysmon)
- Disabled Pre-Authentication Accounts Discovery - PowerShell (Windows Event Log)
- MS Exchange Mailbox Replication service writing Active Server Pages
- Outbound Network Connection from Java Using Default Ports
- RDP Brute-force Detection (Windows Event Log)
- RDP Connection (Sysmon)
- RDP Connection (Windows Event Log)
- RDP Hijacking (Windows Event Log)
- RDP Logon_Logoff Event (Windows Event Log)
- Temporary ConnectWise xml File Activity (Windows Event Log)
- Web or Application Server Spawning a Shell
- Windows MOVEit Transfer Writing ASPX
- Windows PaperCut NG Spawn Shell
- Windows RDPClient Connection Sequence Events