Detect Securityd Memory in CrowdStrike LogScale
An adversary with root access may gather credentials by reading securityd's memory. securityd is a macOS service/daemon responsible for implementing security protocols such as encryption and authorization. A privileged adversary may scan through securityd's memory to find the correct sequence of keys to decrypt the user's logon keychain, yielding various plaintext passwords including user accounts, WiFi, mail, browsers, certificates, and secure notes. In OS X prior to El Capitan, users with root access could read plaintext keychain passwords of logged-in users because Apple's keychain implementation cached these credentials in securityd memory.
MITRE ATT&CK
- Tactic
- Credential Access
- Technique
- T1555 Credentials from Password Stores
- Sub-technique
- T1555.002 Securityd Memory
- Canonical reference
- https://attack.mitre.org/techniques/T1555/002/
LogScale Detection Query
#event_simpleName = "ProcessRollup2"
| FileName = /keychaindump|chainbreaker|keychain-dumper|kcpassword/i
OR CommandLine = /keychaindump|chainbreaker|keychain-dumper|kcpassword/i
OR (FileName = /^(vmmap|lldb|dtrace|heap|sample|leaks|gdb)$/i AND CommandLine = /securityd/i)
OR CommandLine = /task_for_pid.{0,64}securityd/i
| KeychainDumpTool := if(
FileName = /keychaindump|chainbreaker|keychain-dumper|kcpassword/i
OR CommandLine = /keychaindump|chainbreaker|keychain-dumper|kcpassword/i,
1, 0)
| MemoryAccessTool := if(
FileName = /^(vmmap|lldb|dtrace|heap|sample|leaks|gdb)$/i
AND CommandLine = /securityd/i,
1, 0)
| TaskForPid := if(
CommandLine = /task_for_pid.{0,64}securityd/i,
1, 0)
| SuspicionScore := KeychainDumpTool * 3 + MemoryAccessTool * 2 + TaskForPid * 2
| SuspicionScore > 0
| groupBy(
[ComputerName, UserName, FileName, CommandLine, KeychainDumpTool, MemoryAccessTool, TaskForPid, SuspicionScore],
function=[count(as=EventCount), max(@timestamp, as=LastSeen)]
)
| sort(SuspicionScore, order=desc)CrowdStrike LogScale (Falcon) CQL query detecting macOS securityd memory access for credential theft (T1555.002). Queries ProcessRollup2 events for known keychain dump tool names and command line patterns, memory inspection utilities when securityd appears as an argument, and task_for_pid invocations targeting securityd. Applies weighted suspicion scoring (keychain tools 3, memory tools and task_for_pid 2 each) and groups results by host and user to surface repeat activity and prioritise triage.
Data Sources
Required Tables
False Positives & Tuning
- CrowdStrike Falcon Real Time Response (RTR) sessions where analysts invoke memory inspection tools such as vmmap or heap against securityd as part of host-based forensic collection during an incident
- macOS developers or security researchers running lldb debugging sessions on corporate endpoints where securityd is referenced as a target or appears in argument lists during inter-process debugging
- Authorized penetration testing tools pre-approved in Falcon sensor exclusions that happen to match keychain dump tool names or memory inspection patterns against macOS test systems
Other platforms for T1555.002
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 1Run keychaindump to extract credentials from securityd memory
Expected signal: macOS Unified Log: process execution for keychaindump with root privileges. ESF process_exec and task_for_pid events. If SIP is enabled, the command will fail with a permission error — but the attempt is still logged.
- Test 2Attach debugger to securityd process
Expected signal: macOS Unified Log: lldb process creation with securityd PID argument. ESF task_for_pid event from lldb to securityd. If SIP is enabled, lldb will be denied attachment.
- Test 3Map securityd virtual memory with vmmap
Expected signal: macOS Unified Log: vmmap process creation with securityd PID. ESF process execution event. The vmmap output reveals memory layout but does not extract credentials directly.
References (6)
- https://attack.mitre.org/techniques/T1555/002/
- https://web.archive.org/web/20130106164109/https://juusosalonen.com/post/30923743427/breaking-into-the-os-x-keychain
- https://developer.apple.com/library/archive/documentation/Security/Conceptual/Security_Overview/Architecture/Architecture.html
- https://www.welivesecurity.com/2016/07/06/new-osxkeydnap-malware-hungry-credentials/
- https://www.slideshare.net/slideshow/external-to-da-the-os-x-way/62021418
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1555.002/T1555.002.md
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