Network Security & Traffic Analysis

# Network Security & Traffic Analysis

## Purpose

Enable Claude to assist with network security operations including traffic analysis from PCAP files, IDS/IPS rule authoring for Snort and Suricata, firewall rule auditing, network anomaly detection, and network architecture security reviews.

---

## Activation Triggers

This skill activates when the user asks about:
- Analyzing PCAP or PCAPNG files for suspicious activity
- Creating Snort or Suricata detection rules
- Writing Zeek (Bro) scripts for network analysis
- Reviewing firewall rules (iptables, nftables, pf, cloud security groups)
- Detecting C2 beaconing, DNS tunneling, or data exfiltration in network traffic
- Network architecture security review
- IDS/IPS signature development
- Network segmentation and east-west traffic analysis
- TLS inspection and certificate analysis

---

## Prerequisites

```bash
pip install scapy dpkt requests
```

**Recommended tools:**
- `Wireshark / tshark` — Packet capture and GUI analysis
- `Suricata` — Modern IDS/IPS engine
- `Snort 3` — Classic IDS/IPS engine
- `Zeek (Bro)` — Network analysis and scripting framework
- `tcpdump` — Command-line packet capture
- `NetworkMiner` — PCAP artifact extraction
- `nmap` — Network scanning and discovery

---

## Core Capabilities

### 1. PCAP Traffic Analysis

**When the user provides a PCAP file or asks to analyze network traffic:**

```bash
# Quick summary with tshark
tshark -r capture.pcap -q -z io,phs           # Protocol hierarchy
tshark -r capture.pcap -q -z conv,tcp         # TCP conversations
tshark -r capture.pcap -q -z endpoints,ip     # IP endpoints

# Extract HTTP requests
tshark -r capture.pcap -Y http.request -T fields -e ip.src -e http.host -e http.request.uri

# Extract DNS queries
tshark -r capture.pcap -Y dns.flags.response==0 -T fields -e ip.src -e dns.qry.name

# Extract files
tshark -r capture.pcap --export-objects http,./extracted_files/
tshark -r capture.pcap --export-objects smb,./smb_files/

# Run automated analysis
python scripts/pcap_analyzer.py --file capture.pcap --output analysis.json
python scripts/pcap_analyzer.py --file traffic.pcapng --dns --http --top-talkers 20
```

**Traffic Analysis Checklist:**
```
[ ] Protocol distribution — any unexpected protocols?
[ ] Top talkers — unusual source/destination combinations
[ ] DNS analysis — DGA domains, unusually long queries, high volume
[ ] HTTP analysis — suspicious user agents, unusual methods, encoded data
[ ] TLS analysis — invalid certificates, unusual SNI, cert fingerprints
[ ] ICMP analysis — large payloads (tunneling), ping sweeps
[ ] SMB analysis — authentication attempts, file access patterns
[ ] Data volume — large uploads (exfiltration?), irregular transfer sizes
[ ] Timing analysis — regular interval beaconing patterns
```

**Beaconing Detection:**
Beaconing shows as consistent time intervals between outbound connections:
```bash
# tshark: extract connection timestamps to check for regularity
tshark -r capture.pcap -Y "ip.dst == 203.0.113.10 and tcp.flags.syn==1" \
  -T fields -e frame.time_epoch | \
  awk 'NR>1{printf "%.0f\n", ($1-prev)} {prev=$1}' | sort | uniq -c | sort -rn
# Consistent counts at specific intervals = beaconing
```

**DNS Tunneling Detection:**
```bash
# Long DNS query names (>50 chars for subdomain) = likely tunneling
tshark -r capture.pcap -Y "dns.qry.name.len > 50" \
  -T fields -e ip.src -e dns.qry.name | head -50

# High-volume DNS to single domain = tunneling
tshark -r capture.pcap -Y "dns" -T fields -e dns.qry.name | \
  awk -F. '{print $(NF-1)"."$NF}' | sort | uniq -c | sort -rn | head -20
```

### 2. Suricata Rule Creation

**When the user asks to create Suricata IDS rules:**

**Suricata Rule Syntax Reference:**
```
action protocol src_ip src_port -> dst_ip dst_port (options)
```

**Rule Templates:**

```suricata
# Template: C2 Beaconing over HTTP
alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"MALWARE Suspicious C2 Beacon - Regular Interval HTTP POST";
    flow:established,to_server;
    http.method; content:"POST";
    http.uri; content:"/api/check" endswith;
    http.header; content:"User-Agent: Mozilla/4.0 (compatible)";
    threshold:type both, track by_src, count 5, seconds 300;
    classtype:trojan-activity;
    sid:9000001;
    rev:1;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server, attack_target Client_Endpoint,
              created_at 2025_05_28, deployment Perimeter;
)

# Template: DNS Tunneling Detection
alert dns $HOME_NET any -> any any (
    msg:"POLICY Possible DNS Tunneling - Long Subdomain Query";
    dns.query;
    content:".";
    byte_test:1,>,50,0,relative;  # Query length > 50 chars
    threshold:type both, track by_src, count 20, seconds 60;
    classtype:policy-violation;
    sid:9000002;
    rev:1;
)

# Template: Lateral Movement via SMB
alert smb $HOME_NET any -> $HOME_NET 445 (
    msg:"LATERAL-MOVEMENT PsExec Lateral Movement Detected";
    flow:established,to_server;
    content:"PSEXESVC";
    nocase;
    classtype:trojan-activity;
    sid:9000003;
    rev:1;
)

# Template: Data Exfiltration - Large Upload
alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"EXFILTRATION Possible Data Exfiltration - Large HTTP POST";
    flow:established,to_server;
    http.method; content:"POST";
    http.request_body; content:!"";
    dsize:>1000000;   # > 1MB body
    threshold:type both, track by_src, count 3, seconds 300;
    classtype:policy-violation;
    sid:9000004;
    rev:1;
)

# Template: Malicious TLS Certificate (self-signed with suspicious CN)
alert tls $EXTERNAL_NET any -> $HOME_NET any (
    msg:"MALWARE Suspicious TLS Certificate - Self-Signed C2";
    tls.cert_subject; content:"CN=localhost";
    tls.cert_issuer; content:"CN=localhost";
    classtype:trojan-activity;
    sid:9000005;
    rev:1;
)

# Template: Web Shell Access
alert http $EXTERNAL_NET any -> $HOME_NET 80 (
    msg:"WEBSHELL Possible Web Shell Access";
    flow:established,to_server;
    http.uri; content:".php";