Detect Serverless in Google Chronicle
Adversaries may compromise serverless cloud infrastructure, such as Cloudflare Workers, AWS Lambda functions, or Google Apps Scripts, to proxy command-and-control (C2) communications between implants on victim systems and adversary-controlled backend servers. Because traffic destined for compromised serverless functions originates from subdomains of trusted cloud providers (e.g., *.workers.dev, *.execute-api.amazonaws.com, script.google.com), network-layer defenses relying on domain or IP reputation are largely ineffective. Detection pivots to behavioral analysis of victim-side telemetry: identifying processes on endpoints communicating with serverless platforms in patterns consistent with C2 beaconing (periodic connections, low-variance timing, small symmetric payloads), correlating process context with destination domains, and monitoring cloud audit logs for unauthorized modifications to serverless functions within environments the defender controls.
MITRE ATT&CK
- Tactic
- Resource Development
- Technique
- T1584 Compromise Infrastructure
- Sub-technique
- T1584.007 Serverless
- Canonical reference
- https://attack.mitre.org/techniques/T1584/007/
YARA-L Detection Query
rule t1584_007_serverless_c2_beaconing {
meta:
author = "Argus Detection Engineering"
description = "Detects potential C2 beaconing over compromised serverless infrastructure (T1584.007). Identifies hosts making repeated low-volume connections to serverless cloud domains across multiple hours, consistent with implant check-in behavior."
mitre_attack_tactic = "Command and Control"
mitre_attack_technique = "T1584.007"
severity = "HIGH"
priority = "HIGH"
events:
$e.metadata.event_type = "NETWORK_CONNECTION"
$e.network.direction = "OUTBOUND"
(
re.regex($e.target.hostname, `(?i)(.*\.workers\.dev|.*\.cloudflareworkers\.com|.*\.execute-api\.[a-z0-9-]+\.amazonaws\.com|.*\.lambda-url\.[a-z0-9-]+\.amazonaws\.com|script\.google\.com|.*\.cloudfunctions\.net|.*\.run\.app|.*\.azurewebsites\.net|.*\.pages\.dev|.*\.netlify\.app|.*\.vercel\.app|.*\.supabase\.co|.*\.deno\.dev)`) = true
)
$e.principal.ip = $src_ip
$e.target.hostname = $dest_host
$e.principal.process.file.full_path = $proc_path
match:
$src_ip, $dest_host, $proc_path over 24h
outcome:
$event_count = count_distinct($e.metadata.id)
$hour_buckets = count_distinct(timestamp.get_hour($e.metadata.event_timestamp))
$total_bytes_sent = sum($e.network.sent_bytes)
$total_bytes_received = sum($e.network.received_bytes)
$avg_bytes_sent = math.floor(sum($e.network.sent_bytes) / count_distinct($e.metadata.id))
$avg_bytes_received = math.floor(sum($e.network.received_bytes) / count_distinct($e.metadata.id))
$process_name = array_distinct($e.principal.process.file.full_path)
condition:
$event_count >= 12 and
$hour_buckets >= 3 and
$avg_bytes_sent < 4096 and
$avg_bytes_received < 16384
}Chronicle YARA-L 2.0 rule detecting C2 beaconing via serverless cloud infrastructure. Matches outbound network connections to known serverless domains (Cloudflare Workers, AWS Lambda URLs, GCP Cloud Functions, Azure Functions, Vercel, Netlify, etc.), then aggregates per source IP, destination, and process over 24 hours. Fires when connection count exceeds 12 across 3+ hours with payload sizes below C2-consistent thresholds.
Data Sources
Required Tables
False Positives & Tuning
- Corporate developer workstations where engineers frequently test or deploy to personal AWS Lambda or Cloudflare Workers projects during business hours
- Legitimate SaaS integrations where a business application backend regularly calls out to third-party serverless functions for data processing
- Browser-based applications that maintain persistent polling connections to Supabase realtime subscriptions or Vercel Edge Functions
Other platforms for T1584.007
Testing Methodology
Validate this detection against 4 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 1Simulate C2 Beacon to Cloudflare Workers Domain
Expected signal: DeviceNetworkEvents: 15 ConnectionSuccess events from PowerShell.exe to httpbin.org, spaced ~30 seconds apart. Sysmon Event ID 3: Network connections with consistent DestinationPort=443 and DestinationHostname=httpbin.org. Inter-arrival time analysis will show MeanInterval ~30 seconds with low standard deviation (JitterCoefficient < 0.05).
- Test 2Non-Browser Process Connecting to AWS Lambda URL
Expected signal: Sysmon Event ID 3: Network connections with Image=C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe making POST requests to httpbin.org:443. DeviceNetworkEvents: InitiatingProcessFileName=powershell.exe, connection count=5 with small SentBytes values. Sysmon Event ID 22: DNS query for httpbin.org from powershell.exe.
- Test 3Enumerate and Test Unauthorized AWS Lambda Function (Controlled Lab)
Expected signal: AWS CloudTrail: ListFunctions and InvokeFunction API calls logged in CloudTrail with sourceIPAddress of the calling machine, userAgent=aws-cli, and requestParameters including the function name. If forwarded to a SIEM via CloudWatch/Kinesis, these appear in your cloud audit log index. EventName=InvokeFunction with errorCode absent indicates successful invocation.
- Test 4Deploy Test Cloudflare Worker via wrangler CLI (Simulates Infrastructure Compromise Foothold)
Expected signal: Cloudflare Audit Log: Worker script deployment event with actor email, source IP, and timestamp. If Cloudflare Logpush is configured to forward audit logs to your SIEM, the event appears as audit_log.action.type=deploy with resources referencing the worker name. Process telemetry: node.exe or cmd.exe spawning wrangler commands visible in Sysmon Event ID 1.
References (9)
- https://attack.mitre.org/techniques/T1584/007/
- https://www.bleepingcomputer.com/news/security/blackwater-malware-abuses-cloudflare-workers-for-c2-communication/
- https://blog.xpnsec.com/aws-lambda-redirector/
- https://awakesecurity.com/blog/threat-hunting-series-detecting-command-control-in-the-cloud/
- https://www.bleepingcomputer.com/news/security/hackers-abuse-google-apps-script-to-steal-credit-cards-bypass-csp/
- https://docs.aws.amazon.com/lambda/latest/dg/logging-using-cloudtrail.html
- https://developers.cloudflare.com/workers/observability/logging/
- https://cloud.google.com/logging/docs/audit/understanding-audit-logs
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1584.007/T1584.007.md
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