Deobfuscate/Decode Files or Information T1140

Events covered

10 catalog events are tagged with this technique by at least one rule.

Authoring guide

Patterns shared across the 44 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 (30 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 (266 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 (35 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 14 rules

• Base64 Encoded PowerShell Command Detected
• Certutil payload obfuscation (command)
• Certutil payload obfuscation - Tchopper (command)
• DNS-over-HTTPS Enabled by Registry
• MSHTA Execution with Suspicious File Extensions
• Ping Hex IP
• Potential BlackByte Ransomware Activity
• Potential Commandline Obfuscation Using Escape Characters
• PowerShell Base64 Encoded FromBase64String Cmdlet
• PowerShell Decompress Commands
• Suspicious XOR Encoded PowerShell Command
• UNC4841 - Download Compressed Files From Temp.sh Using Wget
• UNC4841 - Download Tar File From Untrusted Direct IP Via Wget
• UNC4841 - SSL Certificate Exfiltration Via Openssl

Elastic 17 rules

• Binary Content Copy via Cmd.exe
• Deprecated - Encoded Executable Stored in the Registry
• Dynamic IEX Reconstruction via Method String Access
• Potential Dynamic IEX Reconstruction via Environment Variables
• Potential PowerShell Obfuscation via Backtick-Escaped Variable Expansion
• Potential PowerShell Obfuscation via Character Array Reconstruction
• Potential PowerShell Obfuscation via Concatenated Dynamic Command Invocation
• Potential PowerShell Obfuscation via High Numeric Character Proportion
• Potential PowerShell Obfuscation via High Special Character Proportion
• Potential PowerShell Obfuscation via Invalid Escape Sequences
• Potential PowerShell Obfuscation via Reverse Keywords
• Potential PowerShell Obfuscation via Special Character Overuse
• Potential PowerShell Obfuscation via String Concatenation
• Potential PowerShell Obfuscation via String Reordering
• PowerShell Obfuscation via Negative Index String Reversal
• Suspicious CertUtil Commands
• Suspicious Windows Powershell Arguments

Splunk 5 rules

• Certutil De-Obfuscate_Decode Files (Sysmon)
• Certutil De-Obfuscate_Decode Files (Windows Event Log)
• Certutil Execution (Sysmon)
• Certutil Execution (Windows Event Log)
• CertUtil With Decode Argument

Kusto 7 rules

• Base64 encoded Windows process command-lines
• Base64 encoded Windows process command-lines (Normalized Process Events)
• Ingress Tool Transfer - Certutil
• NRT Base64 Encoded Windows Process Command-lines
• NRT Process executed from binary hidden in Base64 encoded file
• Process executed from binary hidden in Base64 encoded file
• Qakbot Discovery Activies

YARA-L 1 rule

• MITRE ATT&CK T1140 Encoded Powershell Command