Detect Develop Capabilities in CrowdStrike LogScale
This detection identifies indicators that adversaries have deployed custom-developed capabilities within the target environment. Because T1587 (Develop Capabilities) occurs outside the victim network during the adversary lifecycle, direct detection is impossible; instead, this rule focuses on second-order indicators: unsigned or self-signed executables executing from non-standard paths, low-prevalence binaries making network connections, and novel tooling patterns associated with bespoke malware frameworks. Groups such as Kimsuky, Moonstone Sleet, and Contagious Interview are known to develop custom tools—including malicious NPM packages, spearphishing toolkits, and custom implants—that exhibit these characteristics upon deployment. The detection correlates signature anomalies, environmental prevalence, and behavioral signals to surface likely custom-developed tools used in targeted intrusions.
MITRE ATT&CK
- Tactic
- Resource Development
- Technique
- T1587 Develop Capabilities
- Canonical reference
- https://attack.mitre.org/techniques/T1587/
LogScale Detection Query
// Step 1: Identify unsigned or low-trust process executions from suspicious paths
#event_simpleName=ProcessRollup2
| ImageFileName = /(?i)(\\AppData\\Local\\Temp|\\Downloads|\\ProgramData|C:\\Temp|C:\\Windows\\Temp)/
| ImageFileName != /(?i)(C:\\Windows\\System32|C:\\Windows\\SysWOW64|C:\\Program Files|C:\\Windows\\WinSxS)/
| SignInfoFlags_decimal != 0 // Non-zero indicates signature issues (untrusted, unsigned, invalid)
| select([@timestamp, ComputerName, UserName, ImageFileName, CommandLine, SHA256HashData, TargetProcessId, SignInfoFlags_decimal])
| rename(field=SHA256HashData, as="ProcSHA256")
// Step 2: Join with outbound network connections to external IPs
| join(
{ #event_simpleName=NetworkConnectIP4
| RemoteAddressIP4 != /^(10\.|172\.(1[6-9]|2[0-9]|3[01])\.|192\.168\.|127\.0)/
| select([@timestamp, ComputerName, RemoteAddressIP4, RemotePort, LocalPort, TargetProcessId])
},
field=[ComputerName, TargetProcessId],
include=[RemoteAddressIP4, RemotePort]
)
// Step 3: Aggregate and filter for low-prevalence binaries
| groupBy([ImageFileName, ProcSHA256], function=[
count(ComputerName, distinct=true, as=UniqueHosts),
count(as=EventCount),
collect(ComputerName, limit=5, as=AffectedHosts),
collect(UserName, limit=5, as=Users),
collect(RemoteAddressIP4, limit=10, as=ExternalIPs),
min(@timestamp, as=FirstSeen),
max(@timestamp, as=LastSeen),
take(CommandLine, as=SampleCommandLine)
]
)
| UniqueHosts < 5
| sort(UniqueHosts, order=asc)
| select([ImageFileName, ProcSHA256, UniqueHosts, EventCount, AffectedHosts, Users, ExternalIPs, SampleCommandLine, FirstSeen, LastSeen])CrowdStrike LogScale (Falcon) detection for custom-developed tool deployment (T1587) using Falcon telemetry. Identifies ProcessRollup2 events where executables with non-zero SignInfoFlags (indicating signature anomalies) run from user-writable non-standard paths, then correlates with outbound NetworkConnectIP4 events to external addresses. Filters to low-prevalence binaries (fewer than 5 unique hosts) to surface bespoke implants used by threat groups such as Kimsuky and Moonstone Sleet.
Data Sources
Required Tables
False Positives & Tuning
- Internal developer workstations running self-compiled unsigned tools during development cycles that reach external package registries
- Legitimate third-party security tools (EDR, DLP agents) with non-standard installation paths making cloud telemetry calls
- IT automation scripts deployed to a small pilot group of endpoints reaching cloud management APIs
Other platforms for T1587
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 1Execute Self-Signed Binary from User-Writable Path (Windows)
Expected signal: DeviceProcessEvents: FileName=custom_capability_test.exe, ProcessSignatureStatus=SignedByUntrustedCertificate, FolderPath contains \AppData\Local\Temp. DeviceImageLoadEvents showing DLLs loaded with self-signed parent process.
- Test 2Deploy Malicious NPM Post-Install Script (Cross-Platform)
Expected signal: Sysmon EventCode=1 (Linux auditd execve): process spawned with ParentImage=/usr/bin/node, Image=/bin/sh or /bin/id. audit.log entries showing execve syscall from node process with working directory in node_modules path.
- Test 3Compile and Execute Custom ELF Binary with Network Connection (Linux)
Expected signal: auditd: EXECVE record for /tmp/atomic_custom_tool with ppid matching shell. SOCKADDR audit record showing connect() call to 192.0.2.1:4444. Sysmon for Linux EventCode=3 (Network Connect) if deployed. /proc/<pid>/exe pointing to /tmp path.
References (8)
- https://attack.mitre.org/techniques/T1587/
- https://www.mandiant.com/resources/apt1-exposing-one-of-chinas-cyber-espionage-units
- https://securelist.com/sofacy-apt-hits-high-profile-targets-with-updated-toolset/72924/
- https://www.bitdefender.com/files/News/CaseStudies/study/353/Bitdefender-Whitepaper-StrongPity-APT.pdf
- https://blog.talosintelligence.com/2020/06/promethium-extends-with-strongpity3.html
- https://www.microsoft.com/en-us/security/blog/2024/05/28/moonstone-sleet-emerges-as-new-north-korean-threat-actor/
- https://www.sentinelone.com/labs/contagious-interview-clickfix-reloaded-threat-actor-deploys-new-malware-via-fake-video-conferencing-apps/
- https://virusbulletin.com/virusbulletin/2019/10/kimsuky-apt-group/
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