Wireshark Network Traffic Analysis
Purpose
Execute comprehensive network traffic analysis using Wireshark to capture, filter, and examine network packets for security investigations, performance optimization, and troubleshooting. This skill enables systematic analysis of network protocols, detection of anomalies, and reconstruction of network conversations from PCAP files.
Inputs / Prerequisites
Required Tools
- Wireshark installed (Windows, macOS, or Linux)
- Network interface with capture permissions
- PCAP/PCAPNG files for offline analysis
- Administrator/root privileges for live capture
Technical Requirements
- Understanding of network protocols (TCP, UDP, HTTP, DNS)
- Familiarity with IP addressing and ports
- Knowledge of OSI model layers
- Understanding of common attack patterns
Use Cases
- Network troubleshooting and connectivity issues
- Security incident investigation
- Malware traffic analysis
- Performance monitoring and optimization
- Protocol learning and education
Outputs / Deliverables
Primary Outputs
- Filtered packet captures for specific traffic
- Reconstructed communication streams
- Traffic statistics and visualizations
- Evidence documentation for incidents
Core Workflow
Phase 1: Capturing Network Traffic
Start Live Capture
Begin capturing packets on network interface:
1. Launch Wireshark
2. Select network interface from main screen
3. Click shark fin icon or double-click interface
4. Capture begins immediately
Capture Controls
| Action | Shortcut | Description |
|---|
| Start/Stop Capture | Ctrl+E | Toggle capture on/off |
| Restart Capture | Ctrl+R | Stop and start new capture |
| Open PCAP File | Ctrl+O | Load existing capture file |
| Save Capture | Ctrl+S | Save current capture |
Capture Filters
Apply filters before capture to limit data collection:
# Capture only specific host
host 192.168.1.100
# Capture specific port
port 80
# Capture specific network
net 192.168.1.0/24
# Exclude specific traffic
not arp
# Combine filters
host 192.168.1.100 and port 443
Phase 2: Display Filters
Basic Filter Syntax
Filter captured packets for analysis:
# IP address filters
ip.addr == 192.168.1.1 # All traffic to/from IP
ip.src == 192.168.1.1 # Source IP only
ip.dst == 192.168.1.1 # Destination IP only
# Port filters
tcp.port == 80 # TCP port 80
udp.port == 53 # UDP port 53
tcp.dstport == 443 # Destination port 443
tcp.srcport == 22 # Source port 22
Protocol Filters
Filter by specific protocols:
# Common protocols
http # HTTP traffic
https or ssl or tls # Encrypted web traffic
dns # DNS queries and responses
ftp # FTP traffic
ssh # SSH traffic
icmp # Ping/ICMP traffic
arp # ARP requests/responses
dhcp # DHCP traffic
smb or smb2 # SMB file sharing
TCP Flag Filters
Identify specific connection states:
tcp.flags.syn == 1 # SYN packets (connection attempts)
tcp.flags.ack == 1 # ACK packets
tcp.flags.fin == 1 # FIN packets (connection close)
tcp.flags.reset == 1 # RST packets (connection reset)
tcp.flags.syn == 1 && tcp.flags.ack == 0 # SYN-only (initial connection)
Content Filters
Search for specific content:
frame contains "password" # Packets containing string
http.request.uri contains "login" # HTTP URIs with string
tcp contains "GET" # TCP packets with string
Analysis Filters
Identify potential issues:
tcp.analysis.retransmission # TCP retransmissions
tcp.analysis.duplicate_ack # Duplicate ACKs
tcp.analysis.zero_window # Zero window (flow control)
tcp.analysis.flags # Packets with issues
dns.flags.rcode != 0 # DNS errors
Combining Filters
Use logical operators for complex queries:
# AND operator
ip.addr == 192.168.1.1 && tcp.port == 80
# OR operator
dns || http
# NOT operator
!(arp || icmp)
# Complex combinations
(ip.src == 192.168.1.1 || ip.src == 192.168.1.2) && tcp.port == 443
Phase 3: Following Streams
TCP Stream Reconstruction
View complete TCP conversation:
1. Right-click on any TCP packet
2. Select Follow > TCP Stream
3. View reconstructed conversation
4. Toggle between ASCII, Hex, Raw views
5. Filter to show only this stream
Stream Types
| Stream | Access | Use Case |
|---|
| TCP Stream | Follow > TCP Stream | Web, file transfers, any TCP |
| UDP Stream | Follow > UDP Stream | DNS, VoIP, streaming |
| HTTP Stream | Follow > HTTP Stream | Web content, headers |
| TLS Stream | Follow > TLS Stream | Encrypted traffic (if keys available) |
Stream Analysis Tips
- Review request/response pairs
- Identify transmitted files or data
- Look for credentials in plaintext
- Note unusual patterns or commands
Phase 4: Statistical Analysis
Protocol Hierarchy
View protocol distribution:
Statistics > Protocol Hierarchy
Shows:
- Percentage of each protocol
- Packet counts
- Bytes transferred
- Protocol breakdown tree
Conversations
Analyze communication pairs:
Statistics > Conversations
Tabs:
- Ethernet: MAC address pairs
- IPv4/IPv6: IP address pairs
- TCP: Connection details (ports, bytes, packets)
- UDP: Datagram exchanges
Endpoints
View active network participants:
Statistics > Endpoints
Shows:
- All source/destination addresses
- Packet and byte counts
- Geographic information (if enabled)
Flow Graph
Visualize packet sequence:
Statistics > Flow Graph
Options:
- All packets or displayed only
- Standard or TCP flow
- Shows packet timing and direction
I/O Graphs
Plot traffic over time:
Statistics > I/O Graph
Features:
- Packets per second
- Bytes per second
- Custom filter graphs
- Multiple graph overlays
Phase 5: Security Analysis
Detect Port Scanning
Identify reconnaissance activity:
# SYN scan detection (many ports, same source)
ip.src == SUSPECT_IP && tcp.flags.syn == 1
# Review Statistics > Conversations for anomalies
# Look for single source hitting many destination ports
Identify Suspicious Traffic
Filter for anomalies:
# Traffic to unusual ports
tcp.dstport > 1024 && tcp.dstport < 49152
# Traffic outside trusted network
!(ip.addr == 192.168.1.0/24)
# Unusual DNS queries
dns.qry.name contains "suspicious-domain"
# Large data transfers
frame.len > 1400
ARP Spoofing Detection
Identify ARP attacks:
# Duplicate ARP responses
arp.duplicate-address-frame
# ARP traffic analysis
arp
# Look for:
# - Multiple MACs for same IP
# - Gratuitous ARP floods
# - Unusual ARP patterns
Examine Downloads
Analyze file transfers:
# HTTP file downloads
http.request.method == "GET" && http contains "Content-Disposition"
# Follow HTTP Stream to view file content
# Use File > Export Objects > HTTP to extract files
DNS Analysis
Investigate DNS activity:
# All DNS traffic
dns
# DNS queries only
dns.flags.response == 0
# DNS responses only
dns.flags.response == 1
# Failed DNS lookups
dns.flags.rcode != 0
# Specific domain queries
dns.qry.name contains "domain.com"
Phase 6: Expert Information
Access Expert Analysis
View Wireshark's automated findings:
Analyze > Expert Information
Categories:
- Errors: Critical issues
- Warnings: Potential problems
- Notes: Informational items
- Chats: Normal conversation events
Common Expert Findings
| Finding | Meaning | Action |
|---|
| TCP Retransmission | Packet resent | Check for packet loss |
| Duplicate ACK | Possible loss | Investigate network path |
| Zero Window | Buffer full | Check receiver performance |
| RST | Connection reset | Check for blocks/errors |
| Out-of-Order | Packets reordered | Usually normal, excessive is issue |
Quick Reference
Keyboard Shortcuts
| Action | Shortcut |
|---|
| Open file | Ctrl+O |
| Save file | Ctrl+S |
| Start/Stop capture | Ctrl+E |
| Find packet | Ctrl+F |
| Go to packet | Ctrl+G |
| Next packet | ↓ |
| Previous packet | ↑ |
| First packet | Ctrl+Home |
| Last packet | Ctrl+End |
| Apply filter | Enter |
| Clear filter | Ctrl+Shift+X |
Common Filter Reference
# Web traffic
http || https
# Email
smtp || pop || imap
# File sharing
smb || smb2 || ftp
# Authentication
ldap || kerberos
# Network management
snmp || icmp
# Encrypted
tls || ssl
Export Options
File > Export Specified Packets # Save filtered subset
File > Export Objects > HTTP # Extract HTTP files
File > Export Packet Dissections # Export as text/CSV
Constraints and Guardrails
Operational Boundaries
- Capture only authorized network traffic
- Handle captured data according to privacy policies
- Avoid capturing sensitive credentials unnecessarily
- Properly secure PCAP files containing sensitive data
Technical Limitations
- Large captures consume significant memory
- Encrypted traffic content not visible without keys
- High-speed networks may drop packets
- Some protocols require plugins for full decoding
Best Practices
- Use capture filters to limit data collection
- Save captures regularly during long sessions
- Use display filters rather than deleting packets
- Document analysis findings and methodology
Examples
Example 1: HTTP Credential Analysis
Scenario: Investigate potential plaintext credential transmission
1. Filter: http.request.method == "POST"
2. Look for login forms
3. Follow HTTP Stream
4. Search for username/password parameters
Finding: Credentials transmitted in cleartext form data.
Example 2: Malware C2 Detection
Scenario: Identify command and control traffic
1. Filter: dns
2. Look for unusual query patterns
3. Check for high-frequency beaconing
4. Identify domains with random-looking names
5. Filter: ip.dst == SUSPICIOUS_IP
6. Analyze traffic patterns
Indicators:
- Regular timing intervals
- Encoded/encrypted payloads
- Unusual ports or protocols
Example 3: Network Troubleshooting
Scenario: Diagnose slow web application
1. Filter: ip.addr == WEB_SERVER
2. Check Statistics > Service Response Time
3. Filter: tcp.analysis.retransmission
4. Review I/O Graph for patterns
5. Check for high latency or packet loss
Finding: TCP retransmissions indicating network congestion.
Troubleshooting
No Packets Captured
- Verify correct interface selected
- Check for admin/root permissions
- Confirm network adapter is active
- Disable promiscuous mode if issues persist
Filter Not Working
- Verify filter syntax (red = error)
- Check for typos in field names
- Use Expression button for valid fields
- Clear filter and rebuild incrementally
Performance Issues
- Use capture filters to limit traffic
- Split large captures into smaller files
- Disable name resolution during capture
- Close unnecessary protocol dissectors
Cannot Decrypt TLS/SSL
- Obtain server private key
- Configure at Edit > Preferences > Protocols > TLS
- For ephemeral keys, capture pre-master secret from browser
- Some modern ciphers cannot be decrypted passively
