Q: What is VPC Flow Logs and how do you use it for security investigations?
VPC Flow Logs captures IP traffic information for network interfaces in your VPC. Logged to CloudWatch Logs or S3.
#AWS #Networking & VPC #L2 #Cloud #Infrastructure #S3
🎙️ Candidate Opening & Architectural Context
""In our AWS cloud environment, we managed high-traffic microservices where this exact scenario occurred. When addressing this question, I walk the interviewer through our production incident runbook: isolating the blast radius, checking diagnostic logs and metrics, and applying a safe fix.""
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🛠️ Production Runbook & Step-by-Step Resolution
1️⃣
Initial Diagnostics & Root Cause Analysis
VPC Flow Logs captures IP traffic information for network interfaces in your VPC. Logged to CloudWatch Logs or S3.
- Security investigation — "Where did this attack come from?" Filter logs for a suspicious IP.
- Detecting port scans — many REJECT records from same source IP across many ports.
- Troubleshooting connectivity — if traffic shows REJECT, a security group or NACL is blocking it.
2️⃣
Remediation & Permanent Safeguards
Each record includes: source IP, destination IP, source port, destination port, protocol, bytes, action (ACCEPT/REJECT), etc. Use cases: Query with Athena for large-scale analysis. Set up CloudWatch Logs Insights for real-time querying.
- Billing anomalies — high data transfer costs. Flow logs show which IP is generating the traffic.
💡 The Senior SRE Gold Nugget (Key Architectural Takeaway)
"Pro-Tip: Security investigation — "Where did this attack come from?" Filter logs for a suspicious IP.."
⚡ 60-Second Elevator Pitch Talking Points
- Security investigation — "Where did this attack come from?" Filter logs for a suspicious IP.
- Detecting port scans — many REJECT records from same source IP across many ports.
- Troubleshooting connectivity — if traffic shows REJECT, a security group or NACL is blocking it.
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