Detect Right-to-Left Override in Elastic Security
Adversaries may abuse the right-to-left override (RTLO or RLO) character (U+202E) to disguise a string and/or file name to make it appear benign. RTLO is a non-printing Unicode character that causes the text that follows it to be displayed in reverse. For example, a Windows screensaver executable named 'March 25 \u202Excod.scr' will display as 'March 25 rcs.docx'. Adversaries may abuse the RTLO character as a means of tricking a user into executing what they think is a benign file type. Use of the RTLO character has been seen in many targeted intrusion attempts and criminal activity.
MITRE ATT&CK
- Tactic
- Defense Evasion
- Technique
- T1036 Masquerading
- Sub-technique
- T1036.002 Right-to-Left Override
- Canonical reference
- https://attack.mitre.org/techniques/T1036/002/
Elastic Detection Query
any where event.category in ("process", "file") and (
process.name regex~ ".*\u202e.*" or
process.executable regex~ ".*\u202e.*" or
process.command_line regex~ ".*\u202e.*" or
file.path regex~ ".*\u202e.*" or
file.name regex~ ".*\u202e.*"
)Detects the Right-to-Left Override character (U+202E) in process names, executables, command lines, and file paths using ECS fields. RTLO causes displayed text to appear reversed, enabling adversaries to disguise malicious executables as benign file types (e.g., .exe appearing as .docx).
Data Sources
Required Tables
False Positives & Tuning
- Legitimate Unicode text processing or editor software that handles RTL script file names on multilingual endpoints (Arabic, Hebrew, Farsi locale environments)
- Internationalization QA tooling that generates bidirectional Unicode test file names as part of software testing pipelines
- Security research or red team tooling that intentionally creates RTLO-named test artifacts during authorized penetration testing exercises
Other platforms for T1036.002
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Create File with RTLO Character to Disguise Extension
Expected signal: Sysmon Event ID 11: FileCreate with TargetFilename containing the RTLO character (U+202E). The filename in logs will show the raw Unicode character.
- Test 2Create Executable Masquerading as PDF via RTLO
Expected signal: Sysmon Event ID 11: FileCreate with .scr extension disguised via RTLO. The file appears as 'invoice_2026rcs.pdf' in Explorer but is actually a screensaver executable.
- Test 3RTLO in Registry Value (Windows)
Expected signal: Sysmon Event ID 13: RegistryEvent (Value Set) with the RTLO character in the registry value name. Regedit.exe will display the reversed text but reg.exe will show the raw characters.
References (6)
- https://attack.mitre.org/techniques/T1036/002/
- https://resources.infosecinstitute.com/spoof-using-right-to-left-override-rtlo-technique-2/
- https://blog.trendmicro.com/trendlabs-security-intelligence/plead-targeted-attacks-against-taiwanese-government-agencies-2/
- https://securelist.com/zero-day-vulnerability-in-telegram/83800/
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1036.002/T1036.002.md
- https://github.com/SigmaHQ/sigma/tree/master/rules/windows/file_event
Unlock Pro Content
Get the full detection package for T1036.002 including response playbook, investigation guide, and atomic red team tests.