ATT&CK coverage › Technique
Server Software Component: Web Shell T1505.003
Adversaries may backdoor web servers with web shells to establish persistent access to systems. A Web shell is a Web script that is placed on an openly accessible Web server to allow an adversary to access the Web server as a gateway into a network. A Web shell may provide a set of functions to execute or a command-line interface on the system that hosts the Web server.
Events covered
3 catalog events are tagged with this technique by at least one rule.
| Provider | Event ID | Title |
|---|---|---|
| Sysmon | 1 | Process creation |
| Sysmon | 11 | FileCreate |
| Security-Auditing | 4688 | A new process has been created. |
Authoring guide
Patterns shared across the 16 rules above: which fields they filter on, what specific values they look for, and what they exclude. Field names are normalized 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 (8 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 (212 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.
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 13 rules
- Chopper Webshell Process Pattern
- IIS Native-Code Module Command Line Installation
- Potential Webshell Creation On Static Website
- Suspicious ASPX File Drop by Exchange
- Suspicious Child Process Of SQL Server
- Suspicious File Drop by Exchange
- Suspicious File Write to SharePoint Layouts Directory
- Suspicious File Write to Webapps Root Directory
- Suspicious MSExchangeMailboxReplication ASPX Write
- Suspicious Process By Web Server Process
- Webshell Detection With Command Line Keywords
- Webshell Hacking Activity Patterns
- Webshell Tool Reconnaissance Activity