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---
name: analyzing-network-traffic-of-malware
description: 'Analyzes network traffic generated by malware during sandbox execution
or live incident response to identify C2 protocols, data exfiltration channels,
payload downloads, and lateral movement patterns using Wireshark, Zeek, and Suricata.
Activates for requests involving malware network analysis, C2 traffic decoding,
malware PCAP analysis, or network-based malware detection.
'
domain: cybersecurity
subdomain: malware-analysis
tags:
- malware
- network-analysis
- PCAP
- Wireshark
- C2-detection
version: 1.0.0
author: mahipal
license: Apache-2.0
nist_csf:
- DE.AE-02
- RS.AN-03
- ID.RA-01
- DE.CM-01
mitre_attack:
- T1071.001
- T1571
- T1573
- T1095
---
# Analyzing Network Traffic of Malware
## When to Use
- Sandbox execution has captured a PCAP file and the network behavior needs detailed analysis
- Identifying the C2 protocol structure for writing network detection signatures
- Determining what data the malware exfiltrates and to which external infrastructure
- Analyzing DNS tunneling, domain generation algorithms (DGA), or fast-flux behavior
- Creating Suricata/Snort signatures based on observed malware network patterns
**Do not use** for host-based analysis of malware behavior; use Cuckoo sandbox reports or Volatility memory analysis for process-level activity.
## Prerequisites
- Wireshark 4.x installed for interactive PCAP analysis
- tshark (Wireshark CLI) for scripted packet extraction
- Zeek installed for automated metadata generation from PCAPs
- Suricata with ET Open/ET Pro rulesets for signature matching
- NetworkMiner for file extraction and credential detection from PCAPs
- Python 3.8+ with `scapy` and `dpkt` for programmatic packet analysis
## Workflow
### Step 1: Initial PCAP Overview
Get a high-level understanding of the network traffic:
```bash
# Capture statistics
capinfos malware.pcap
# Protocol hierarchy
tshark -r malware.pcap -q -z io,phs
# Endpoint statistics (top talkers)
tshark -r malware.pcap -q -z endpoints,ip
# Conversation statistics
tshark -r malware.pcap -q -z conv,tcp
# DNS query summary
tshark -r malware.pcap -q -z dns,tree
```
### Step 2: Analyze DNS Activity
Examine DNS queries for DGA, tunneling, or C2 domain resolution:
```bash
# Extract all DNS queries
tshark -r malware.pcap -T fields -e frame.time -e dns.qry.name -e dns.a \
-Y "dns.flags.response == 1" | sort
# Detect DGA patterns (high entropy domain names)
python3 << 'PYEOF'
import math
from collections import Counter
def entropy(s):
p = [n/len(s) for n in Counter(s).values()]
return -sum(pi * math.log2(pi) for pi in p if pi > 0)
# Parse DNS queries from tshark output
import subprocess
result = subprocess.run(
["tshark", "-r", "malware.pcap", "-T", "fields", "-e", "dns.qry.name",
"-Y", "dns.flags.response == 0"],
capture_output=True, text=True
)
domains = set(result.stdout.strip().split('\n'))
print("Suspicious DNS queries (high entropy):")
for domain in domains:
if domain:
subdomain = domain.split('.')[0]
ent = entropy(subdomain)
if ent > 3.5 and len(subdomain) > 10:
print(f" {domain} (entropy: {ent:.2f})")
PYEOF
# Detect DNS tunneling (large TXT responses)
tshark -r malware.pcap -T fields -e dns.qry.name -e dns.txt \
-Y "dns.resp.type == 16 and dns.resp.len > 100"
```
### Step 3: Analyze HTTP/HTTPS C2 Communication
Examine web-based command-and-control traffic:
```bash
# Extract HTTP requests
tshark -r malware.pcap -T fields \
-e frame.time -e ip.src -e ip.dst -e http.host \
-e http.request.method -e http.request.uri -e http.user_agent \
-Y "http.request"
# Extract HTTP response bodies (potential payload downloads)
tshark -r malware.pcap -T fields \
-e http.host -e http.request.uri -e http.content_type -e tcp.len \
-Y "http.response and tcp.len > 1000"
# Extract POST data (potential exfiltration)
tshark -r malware.pcap -T fields \
-e http.host -e http.request.uri -e http.file_data \
-Y "http.request.method == POST"
# TLS analysis (SNI, JA3 fingerprints)
tshark -r malware.pcap -T fields \
-e tls.handshake.extensions_server_name \
-e tls.handshake.ja3 \
-Y "tls.handshake.type == 1"
# Extract TLS certificate details
tshark -r malware.pcap -T fields \
-e x509ce.dNSName -e x509af.serialNumber \
-e x509sat.utf8String \
-Y "tls.handshake.type == 11"
# Export HTTP objects (downloaded files)
tshark -r malware.pcap --export-objects http,exported_files/
```
### Step 4: Detect Beaconing Patterns
Identify regular periodic communication indicating C2 beaconing:
```python
# Beacon detection from PCAP
from scapy.all import rdpcap, IP, TCP
from collections import defaultdict
import statistics
packets = rdpcap("malware.pcap")
# Group connections by destination IP:port
connections = defaultdict(list)
for pkt in packets:
if IP in pkt and TCP in pkt:
if pkt[TCP].flags & 0x02: # SYN flag
dst = f"{pkt[IP].dst}:{pkt[TCP].dport}"
connections[dst].append(float(pkt.time))
# Analyze timing intervals for beaconing
print("Beacon Analysis:")
for dst, times in connections.items():
if len(times) >= 5:
intervals = [times[i+1] - times[i] for i in range(len(times)-1)]
avg = statistics.mean(intervals)
stdev = statistics.stdev(intervals) if len(intervals) > 1 else 0
jitter = (stdev / avg * 100) if avg > 0 else 0
if 10 < avg < 3600 and jitter < 30: # Regular interval with < 30% jitter
print(f" [!] {dst}: {len(times)} connections")
print(f" Interval: {avg:.1f}s ± {stdev:.1f}s (jitter: {jitter:.1f}%)")
print(f" Pattern: LIKELY BEACONING")
```
### Step 5: Generate Network Detection Signatures
Create Suricata/Snort rules from observed traffic patterns:
```bash
# Run Suricata against the PCAP for existing signature matches
suricata -r malware.pcap -l suricata_output/ -c /etc/suricata/suricata.yaml
# Review alerts
cat suricata_output/fast.log
# Create custom Suricata rule from observed patterns
cat << 'EOF' > custom_malware.rules
# C2 beacon detection based on observed URI pattern
alert http $HOME_NET any -> $EXTERNAL_NET any (
msg:"MALWARE MalwareX C2 Beacon";
flow:established,to_server;
http.method; content:"POST";
http.uri; content:"/gate.php?id=";
http.user_agent; content:"Mozilla/5.0 (compatible; MSIE 10.0)";
sid:9000001; rev:1;
)
# DNS query for known C2 domain
alert dns $HOME_NET any -> any any (
msg:"MALWARE MalwareX C2 DNS Query";
dns.query; content:"update.malicious.com";
sid:9000002; rev:1;
)
# JA3 hash match for malware TLS client
alert tls $HOME_NET any -> $EXTERNAL_NET any (
msg:"MALWARE MalwareX JA3 Match";
ja3.hash; content:"a0e9f5d64349fb13191bc781f81f42e1";
sid:9000003; rev:1;
)
EOF
```
### Step 6: Extract Files and Artifacts from Traffic
Recover transferred files and embedded data:
```bash
# Extract files using Zeek
zeek -r malware.pcap /opt/zeek/share/zeek/policy/frameworks/files/extract-all-files.zeek
ls extract_files/
# Extract files using NetworkMiner (GUI)
# Or use tshark for specific protocol exports
tshark -r malware.pcap --export-objects http,http_objects/
tshark -r malware.pcap --export-objects smb,smb_objects/
tshark -r malware.pcap --export-objects tftp,tftp_objects/
# Hash all extracted files
sha256sum http_objects/* smb_objects/* 2>/dev/null
# Generate Zeek logs for comprehensive metadata
zeek -r malware.pcap
# Output: conn.log, dns.log, http.log, ssl.log, files.log, etc.
```
## Key Concepts
| Term | Definition |
|------|------------|
| **Beaconing** | Regular periodic connections from malware to C2 server, identifiable by consistent time intervals and packet sizes |
| **JA3/JA3S** | TLS fingerprinting method creating a hash from ClientHello/ServerHello parameters to uniquely identify malware TLS implementations |
| **DGA (Domain Generation Algorithm)** | Algorithm generating pseudo-random domain names that malware queries to locate C2 servers, evading static domain blocklists |
| **DNS Tunneling** | Encoding data in DNS queries and responses to establish a C2 channel or exfiltrate data through DNS infrastructure |
| **Fast Flux** | DNS technique rapidly rotating IP addresses for a domain to avoid takedown and distribute C2 across many compromised hosts |
| **SNI (Server Name Indication)** | TLS extension revealing the hostname the client is connecting to; visible even in encrypted HTTPS connections |
| **Network Signature** | Suricata/Snort rule matching specific patterns in network traffic (headers, payloads, timing) to detect malicious communications |
## Tools & Systems
- **Wireshark**: Open-source packet analyzer for deep interactive inspection of network traffic at the protocol level
- **Zeek**: Network analysis framework generating structured metadata logs (conn, dns, http, ssl) from live or captured traffic
- **Suricata**: High-performance network IDS/IPS for signature-based detection with Lua scripting for custom detection logic
- **NetworkMiner**: Network forensic analysis tool for extracting files, images, and credentials from PCAP files
- **Scapy**: Python packet manipulation library for programmatic packet analysis, beacon detection, and protocol decoding
## Common Scenarios
### Scenario: Decoding a Custom Binary C2 Protocol
**Context**: Malware communicates with its C2 server using a custom binary protocol over TCP port 8443. Standard HTTP analysis yields no results. The protocol structure needs to be reverse engineered from the PCAP.
**Approach**:
1. Filter the PCAP for TCP port 8443 conversations and follow the TCP stream
2. Identify the message framing (length prefix, delimiter, fixed-size headers)
3. Compare multiple messages to identify static header fields vs variable data fields
4. Cross-reference with reverse engineering findings from Ghidra (if the binary was analyzed)
5. Write a Wireshark dissector or Scapy parser for the custom protocol
6. Create Suricata rules matching the static header bytes for network detection
7. Document the full protocol specification for threat intelligence sharing
**Pitfalls**:
- Analyzing only the first few packets; some C2 protocols change behavior after initial handshake
- Not decrypting TLS traffic when the sandbox has MITM capabilities
- Confusing legitimate CDN or cloud traffic with C2 (validate destination IPs)
- Missing C2 traffic that uses DNS or ICMP instead of TCP/UDP
## Output Format
```
MALWARE NETWORK TRAFFIC ANALYSIS
===================================
PCAP File: malware_sandbox.pcap
Duration: 300 seconds
Total Packets: 12,847
Total Bytes: 4.2 MB
DNS ACTIVITY
Total Queries: 47
DGA Detected: Yes (23 high-entropy queries to .com TLD)
Tunneling: No
Resolved C2: update.malicious[.]com -> 185.220.101[.]42
C2 COMMUNICATION
Protocol: HTTPS (TLS 1.2)
Server: 185.220.101[.]42:443
SNI: update.malicious[.]com
JA3 Hash: a0e9f5d64349fb13191bc781f81f42e1
Beacon Interval: 60.2s ± 6.8s (11.3% jitter)
Total Sessions: 237
Data Sent: 147 MB
Data Received: 2.3 MB
Certificate: CN=update.malicious[.]com (self-signed, expired)
PAYLOAD DOWNLOADS
GET /payload.dll from compromised-site[.]com
Size: 98,304 bytes
SHA-256: abc123def456...
Content-Type: application/octet-stream
EXFILTRATION
Method: HTTPS POST to /gate.php
Content-Type: application/octet-stream
Average Size: 15,432 bytes per request
Total Volume: 147 MB over 4 hours
SURICATA ALERTS
[1:2028401] ET MALWARE Generic C2 Beacon Pattern
[1:2028500] ET POLICY Self-Signed Certificate
GENERATED SIGNATURES
SID 9000001: MalwareX HTTP beacon pattern
SID 9000002: MalwareX DNS C2 domain
SID 9000003: MalwareX JA3 TLS fingerprint
```

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# API Reference: Malware Network Traffic Analysis
## dpkt - Python Packet Parsing
### PCAP Reading
```python
import dpkt
with open("malware.pcap", "rb") as f:
pcap = dpkt.pcap.Reader(f)
for ts, buf in pcap:
eth = dpkt.ethernet.Ethernet(buf)
ip = eth.data
tcp = ip.data
```
### HTTP Parsing
```python
http_req = dpkt.http.Request(tcp.data)
http_req.method # GET, POST
http_req.uri # Request URI
http_req.headers # Header dict
http_req.body # POST body
http_resp = dpkt.http.Response(tcp.data)
http_resp.status # Status code
http_resp.body # Response body
```
### IP Address Conversion
```python
dpkt.utils.inet_to_str(ip.src) # bytes -> "1.2.3.4"
dpkt.utils.inet_aton("1.2.3.4") # "1.2.3.4" -> bytes
```
## Wireshark Display Filters for Malware
### C2 Detection
```
http.request.method == "POST" && http.content_length > 0
tls.handshake.type == 1 # TLS Client Hello
tcp.flags.syn == 1 && tcp.flags.ack == 0 # New connections
dns.qry.type == 16 # TXT records
```
### Payload Analysis
```
tcp.payload contains "MZ" # PE downloads
http.response.code == 200 && http.content_type contains "octet"
frame.len > 1400 # Large packets
```
## tshark - Field Extraction
### HTTP Requests
```bash
tshark -r malware.pcap -Y "http.request" -T fields \
-e http.request.method -e http.host -e http.request.uri \
-e http.user_agent -e http.content_length
```
### TLS/JA3 Fingerprinting
```bash
tshark -r malware.pcap -Y "tls.handshake.type==1" -T fields \
-e ip.src -e ip.dst -e tls.handshake.ja3
```
### DNS Queries
```bash
tshark -r malware.pcap -Y "dns.qr==0" -T fields \
-e ip.src -e dns.qry.name -e dns.qry.type
```
### Stream Follow
```bash
tshark -r malware.pcap -z follow,tcp,ascii,0
tshark -r malware.pcap -z follow,http,ascii,0
```
## Suricata Rule Syntax
### HTTP Rules
```
alert http $HOME_NET any -> $EXTERNAL_NET any (
msg:"MALWARE C2 Beacon";
flow:established,to_server;
http.method; content:"POST";
http.uri; content:"/gate.php";
sid:9000001; rev:1;
)
```
### DNS Rules
```
alert dns $HOME_NET any -> any any (
msg:"MALWARE DNS Tunneling";
dns.query; pcre:"/^[a-z0-9]{20,}\./";
threshold:type threshold, track by_src, count 10, seconds 60;
sid:9000002; rev:1;
)
```
### TLS Rules
```
alert tls $HOME_NET any -> $EXTERNAL_NET any (
msg:"MALWARE JA3 Match";
ja3.hash; content:"a0e9f5d64349fb13191bc781f81f42e1";
sid:9000003; rev:1;
)
```
## RITA - Beacon Analysis
### Syntax
```bash
rita import zeek_logs dataset_name
rita analyze dataset_name
rita show-beacons dataset_name
rita show-long-connections dataset_name
rita show-dns-fqdn-lengths dataset_name
```
## NetworkMiner
### CLI Syntax
```bash
NetworkMiner --inputfile malware.pcap --outputdir /tmp/extracted
```
Extracts files, sessions, credentials, DNS from PCAP

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#!/usr/bin/env python3
"""Malware network traffic analysis agent for C2 protocol decoding and signature generation."""
import os
import sys
import math
from collections import defaultdict, Counter
try:
import dpkt
HAS_DPKT = True
except ImportError:
HAS_DPKT = False
try:
from scapy.all import rdpcap, IP, TCP, DNS, DNSQR
HAS_SCAPY = True
except ImportError:
HAS_SCAPY = False
def shannon_entropy(data):
"""Calculate Shannon entropy of byte data."""
if not data:
return 0.0
counter = Counter(data)
length = len(data)
return -sum((c / length) * math.log2(c / length) for c in counter.values())
def extract_tcp_streams(pcap_path):
"""Extract TCP stream payloads grouped by conversation."""
if not HAS_DPKT:
return {}
streams = defaultdict(list)
with open(pcap_path, "rb") as f:
pcap = dpkt.pcap.Reader(f)
for ts, buf in pcap:
try:
eth = dpkt.ethernet.Ethernet(buf)
if not isinstance(eth.data, dpkt.ip.IP):
continue
ip = eth.data
if not isinstance(ip.data, dpkt.tcp.TCP):
continue
tcp = ip.data
if len(tcp.data) > 0:
src = f"{dpkt.utils.inet_to_str(ip.src)}:{tcp.sport}"
dst = f"{dpkt.utils.inet_to_str(ip.dst)}:{tcp.dport}"
key = tuple(sorted([src, dst]))
streams[key].append({
"ts": ts,
"src": src,
"dst": dst,
"data": tcp.data,
"data_len": len(tcp.data),
})
except Exception:
continue
return streams
def analyze_payload_structure(payloads):
"""Analyze payload structure to identify protocol framing."""
if not payloads:
return {}
analysis = {
"total_payloads": len(payloads),
"sizes": [len(p) for p in payloads],
"avg_size": sum(len(p) for p in payloads) / len(payloads),
"entropy_values": [],
}
for p in payloads[:20]:
ent = shannon_entropy(p)
analysis["entropy_values"].append(round(ent, 4))
avg_ent = sum(analysis["entropy_values"]) / len(analysis["entropy_values"])
analysis["avg_entropy"] = round(avg_ent, 4)
analysis["likely_encrypted"] = avg_ent > 7.5
# Check for common header patterns
first_bytes = [p[:4] for p in payloads if len(p) >= 4]
if first_bytes:
byte_counter = Counter([b.hex() for b in first_bytes])
most_common = byte_counter.most_common(3)
analysis["common_headers"] = [
{"hex": h, "count": c} for h, c in most_common
]
return analysis
def detect_dns_tunneling(pcap_path, entropy_threshold=3.5):
"""Detect DNS tunneling in malware traffic."""
if not HAS_SCAPY:
return []
packets = rdpcap(pcap_path)
suspicious = []
for pkt in packets:
if DNS in pkt and pkt[DNS].qr == 0 and DNSQR in pkt:
qname = pkt[DNSQR].qname.decode("utf-8", errors="replace").rstrip(".")
parts = qname.split(".")
if len(parts) > 2:
subdomain = ".".join(parts[:-2])
ent = shannon_entropy(subdomain.encode())
if ent > entropy_threshold or len(subdomain) > 50:
suspicious.append({
"query": qname,
"subdomain_length": len(subdomain),
"entropy": round(ent, 4),
"src": pkt[IP].src if IP in pkt else "?",
"qtype": pkt[DNSQR].qtype,
})
return suspicious
def detect_dga_domains(pcap_path, min_length=12, entropy_threshold=3.5):
"""Detect DGA (Domain Generation Algorithm) domains."""
if not HAS_SCAPY:
return []
packets = rdpcap(pcap_path)
dga_suspects = []
for pkt in packets:
if DNS in pkt and pkt[DNS].qr == 0 and DNSQR in pkt:
qname = pkt[DNSQR].qname.decode("utf-8", errors="replace").rstrip(".")
parts = qname.split(".")
if len(parts) >= 2:
sld = parts[-2]
if len(sld) >= min_length:
ent = shannon_entropy(sld.encode())
if ent > entropy_threshold:
dga_suspects.append({
"domain": qname,
"sld": sld,
"length": len(sld),
"entropy": round(ent, 4),
})
return dga_suspects
def extract_http_c2(pcap_path):
"""Extract HTTP-based C2 communication patterns."""
if not HAS_DPKT:
return []
requests = []
with open(pcap_path, "rb") as f:
pcap = dpkt.pcap.Reader(f)
for ts, buf in pcap:
try:
eth = dpkt.ethernet.Ethernet(buf)
if not isinstance(eth.data, dpkt.ip.IP):
continue
ip = eth.data
if not isinstance(ip.data, dpkt.tcp.TCP):
continue
tcp = ip.data
if len(tcp.data) > 0:
try:
http = dpkt.http.Request(tcp.data)
requests.append({
"timestamp": ts,
"src": dpkt.utils.inet_to_str(ip.src),
"dst": dpkt.utils.inet_to_str(ip.dst),
"method": http.method,
"uri": http.uri,
"host": http.headers.get("host", ""),
"user_agent": http.headers.get("user-agent", ""),
"content_type": http.headers.get("content-type", ""),
"body_size": len(http.body) if http.body else 0,
"body_entropy": round(shannon_entropy(http.body), 4) if http.body else 0,
})
except (dpkt.dpkt.NeedData, dpkt.dpkt.UnpackError):
pass
except Exception:
continue
return requests
def generate_suricata_signatures(http_requests, dns_tunneling):
"""Generate Suricata IDS signatures from observed malware network patterns."""
rules = []
sid = 9100000
seen_uris = set()
for req in http_requests:
if req["uri"] not in seen_uris:
seen_uris.add(req["uri"])
rules.append(
f'alert http $HOME_NET any -> $EXTERNAL_NET any ('
f'msg:"MALWARE Suspected C2 HTTP {req["method"]} {req["uri"][:30]}"; '
f'flow:established,to_server; '
f'http.method; content:"{req["method"]}"; '
f'http.uri; content:"{req["uri"]}"; '
f'sid:{sid}; rev:1;)'
)
sid += 1
if dns_tunneling:
domains = set()
for t in dns_tunneling:
parts = t["query"].split(".")
if len(parts) >= 2:
domains.add(".".join(parts[-2:]))
for domain in list(domains)[:5]:
rules.append(
f'alert dns $HOME_NET any -> any any ('
f'msg:"MALWARE DNS Tunneling to {domain}"; '
f'dns.query; content:"{domain}"; nocase; '
f'sid:{sid}; rev:1;)'
)
sid += 1
return rules
if __name__ == "__main__":
print("=" * 60)
print("Malware Network Traffic Analysis Agent")
print("C2 protocol decoding, DNS tunneling, DGA detection")
print("=" * 60)
pcap = sys.argv[1] if len(sys.argv) > 1 else None
if pcap and os.path.exists(pcap):
print(f"\n[*] Analyzing: {pcap}")
print("\n--- HTTP C2 Communication ---")
http_reqs = extract_http_c2(pcap)
for r in http_reqs[:10]:
print(f" {r['method']} {r['host']}{r['uri']} "
f"(body={r['body_size']}B, entropy={r['body_entropy']})")
print("\n--- DNS Tunneling Detection ---")
tunneling = detect_dns_tunneling(pcap)
for t in tunneling[:10]:
print(f" [!] {t['query']} (len={t['subdomain_length']}, ent={t['entropy']})")
print("\n--- DGA Domain Detection ---")
dga = detect_dga_domains(pcap)
for d in dga[:10]:
print(f" [!] {d['domain']} (sld_len={d['length']}, ent={d['entropy']})")
print("\n--- Generated Suricata Rules ---")
rules = generate_suricata_signatures(http_reqs, tunneling)
for r in rules[:5]:
print(f" {r}")
else:
print(f"\n[DEMO] Usage: python agent.py <malware_traffic.pcap>")