Web Service T1102
Tactic: Command & Control
Adversaries may use an existing, legitimate external Web service as a means for relaying data to/from a compromised system. Popular websites, cloud services, and social media acting as a mechanism for C2 may give a significant amount of cover due to the likelihood that hosts within a network are already communicating with them prior to a compromise. Using common services, such as those offered by Google, Microsoft, or Twitter, makes it easier for adversaries to hide in expected noise. Web service providers commonly use SSL/TLS encryption, giving adversaries an added level of protection.
Events covered
8 catalog events are tagged with this technique by at least one rule.
| Provider | Event | Title |
|---|---|---|
| Sysmon | Event ID 1 | Process creation |
| Sysmon | Event ID 3 | Network connection |
| Sysmon | Event ID 22 | DNSEvent (DNS query) |
| Security-Auditing | Event ID 4688 | A new process has been created. |
| ESF | exec | Process Execution (Notify) |
| ESF | fork | Process Fork (Notify) |
| ESF | write | File Write (NOTIFY) |
| Sysmon-for-Linux | Event ID 3 | Network connection |
Authoring guide
Patterns shared across the 59 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 (61 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 (1054 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 (301 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 19 rules
- Cloudflared Tunnel Connections Cleanup
- Cloudflared Tunnel Execution
- Communication To LocaltoNet Tunneling Service Initiated
- Communication To LocaltoNet Tunneling Service Initiated - Linux
- Communication To Ngrok Tunneling Service - Linux
- Communication To Ngrok Tunneling Service Initiated
- Github Self-Hosted Runner Execution
- Network Connection Initiated To AzureWebsites.NET By Non-Browser Process
- New Connection Initiated To Potential Dead Drop Resolver Domain
- Potentially Suspicious Azure Front Door Connection
- Potentially Suspicious Network Connection To Notion API
- Process Initiated Network Connection To Ngrok Domain
- PwnDrp Access
- Raw Paste Service Access
- Suspicious Child Process Of Manage Engine ServiceDesk
- Suspicious Non-Browser Network Communication With Google API
- Suspicious Non-Browser Network Communication With Telegram API
- Telegram API Access
- Telegram Bot API Request
Elastic 18 rules
- AWS CLI Command with Custom Endpoint URL
- AWS SNS Rare Protocol Subscription by User
- AWS SNS Topic Message Publish by Rare User
- Connection to Common Large Language Model Endpoints
- Connection to Commonly Abused Web Services
- DNS to Commonly Abused Web Services
- Google Calendar C2 via Script Interpreter
- Linux Telegram API Request
- Network Connection to OAST Domain via Script Interpreter
- Potential Etherhiding C2 via Blockchain Connection
- Statistical Model Detected C2 Beaconing Activity
- Statistical Model Detected C2 Beaconing Activity with High Confidence
- Suspicious AWS S3 Connection via Script Interpreter
- Suspicious Curl to Google App Script Endpoint
- Suspicious File Downloaded from Google Drive
- Uncommon DNS Request via Bun or Node.js
- Unusual Network Connection to Suspicious Web Service
- Unusual Web Request
Splunk 6 rules
- Linux Ngrok Reverse Proxy Usage
- Ngrok Reverse Proxy on Network
- Potential Telegram API Request Via CommandLine
- Windows Abused Web Services
- Windows DNS Query Request by Telegram Bot API
- Windows Ngrok Reverse Proxy Usage
Kusto 16 rules
- A host is potentially running a hacking tool (ASIM Web Session schema)
- ApexOne - Suspicious connections
- Cisco Cloud Security - Hack Tool User-Agent Detected
- Cisco SE - Possible webshell
- Cisco WSA - Multiple errors to resource from risky category
- Cisco WSA - Multiple errors to URL
- Cisco WSA - Unexpected URL
- CreepyDrive request URL sequence
- CreepyDrive URLs
- Detect requests for an uncommon resources on the web (ASIM Web Session)
- Ngrok Reverse Proxy on Network (ASIM DNS Solution)
- NRT Squid proxy events related to mining pools
- Possible Phishing with CSL and Network Sessions
- Powershell Empire Cmdlets Executed in Command Line
- Request for single resource on domain
- Squid proxy events related to mining pools