Protocol Analyzer Outputs for Forensics#

In the world of digital forensics and cybersecurity, the ability to uncover and identify network-based threats is of paramount importance. Network attacks, whether they are attempts to compromise data integrity, steal sensitive information, or disrupt critical services, pose significant risks to organizations and individuals alike. To effectively investigate and mitigate such threats, digital forensic investigators rely on a powerful tool in their arsenal: the protocol analyzer.

Protocol analyzers, often referred to as network packet analyzers or sniffers, provide investigators with a unique window into the intricate world of network communications. These tools capture and analyze the packets traversing a network, allowing forensic experts to decipher the nuances of data exchanges, detect anomalies, and pinpoint the presence of malicious activities. In this discussion, we take a look at the valuable role of protocol analyzers in digital investigations, exploring how they contribute to the identification and understanding of common network attacks. We will examine real-world examples of network attacks and showcase how protocol analyzer output can be instrumental in unraveling the intricacies of these threats.

What a Protocol Analyzer Adds to Digital Investigations#

A protocol analyzer, also known as a network packet analyzer or network sniffer, is a valuable tool in digital forensic investigations, particularly in the realm of network security. It offers several key contributions to investigations:

  • Traffic Analysis: Protocol analyzers capture and analyze network traffic, providing insights into communication patterns, data exchanges, and the behavior of devices on a network. This helps investigators understand what normal network traffic looks like.

  • Anomaly Detection: By comparing current network traffic to established baselines, protocol analyzers can flag unusual or suspicious patterns. This is crucial for identifying potential security breaches or network attacks.

  • Evidence Collection: In digital forensics, network packet captures serve as valuable evidence. They can be used to reconstruct network activities, verify or refute claims, and establish a timeline of events during an incident.

  • Attack Identification: Protocol analyzers can help investigators identify specific network attacks, as they capture the packets that constitute the attack traffic. This is particularly useful for recognizing known attack signatures or patterns.

Now, let’s look at some common network attacks and provide examples of how to identify them using protocol analyzer output - in our examples, were using tcpdump, but the same principles apply regardless of your choice of analyzer.

DDoS (Distributed Denial of Service) Attack#

DDoS attacks involve overwhelming a target system or network with a flood of traffic, rendering it unavailable to legitimate users.

In tcpdump, you might observe a sharp increase in incoming traffic to a specific server or IP address. The traffic volume will exceed normal levels, often with a high number of connection requests. Additionally, you may see repeated identical requests from various source IPs, indicating a distributed attack.

10:45:03.556123 IP source_ip.12345 > target_ip.80: SYN,ACK, ACK
10:45:03.556124 IP source_ip.12346 > target_ip.80: SYN,ACK, ACK
10:45:03.556125 IP source_ip.12347 > target_ip.80: SYN,ACK, ACK
...

Port Scanning Attack#

Port scanning involves probing a target network to identify open ports and services, which can be used for reconnaissance or exploitation.

In tcpdump, you may notice a series of connection attempts to various ports on a target system. Port scanning often involves TCP SYN packets to check for open ports. Frequent and rapid connection attempts to multiple ports from a single source IP may indicate a scanning attempt.

10:30:01.123456 IP source_ip.12345 > target_ip.22: SYN
10:30:01.123457 IP source_ip.12346 > target_ip.80: SYN
10:30:01.123458 IP source_ip.12347 > target_ip.443: SYN
...

Brute Force Attack#

Brute force attacks involve attempting to gain unauthorized access by systematically trying different combinations of usernames and passwords.

Tcpdump can capture login attempts where multiple login requests are sent to a target server with different username and password combinations. These login attempts may appear as a series of authentication failures in the packet capture.

10:20:15.987654 IP source_ip.12345 > target_ip.22: SSH authentication failure
10:20:15.987655 IP source_ip.12346 > target_ip.22: SSH authentication failure
10:20:15.987656 IP source_ip.12347 > target_ip.22: SSH authentication failure
...

SQL Injection Attack#

SQL injection attacks occur when an attacker injects malicious SQL code into input fields or parameters to manipulate a database, potentially extracting sensitive data or compromising the database.

In tcpdump captures, SQL injection attempts may manifest as unusually crafted HTTP requests or POST data. Look for suspicious input data that includes SQL syntax, such as UNION SELECT statements or escape characters.

10:55:22.123456 IP source_ip.12345 > target_ip.80: POST /login.php HTTP/1.1
10:55:22.123457 IP source_ip.12345 > target_ip.80: SQL injection payload: ' OR '1'='1

Man-in-the-Middle (MitM) Attack#

MitM attacks involve intercepting and eavesdropping on communication between two parties without their knowledge. Attackers may also modify data in transit.

Suspicious MitM activity can be identified in tcpdump by observing abnormal routing or the presence of unauthorized devices. Look for ARP poisoning or ICMP redirection packets that suggest an attacker is intercepting traffic.

10:40:11.987654 IP source_ip.12345 > target_ip.80: TCP
10:40:11.987655 IP attacker_ip > source_ip: ICMP Redirect

Phishing Attack#

Phishing attacks involve tricking users into revealing sensitive information, such as login credentials or financial data, by impersonating a trustworthy entity.

Tcpdump can capture phishing attempts as part of email or web traffic. Look for suspicious URLs or email headers that mimic well-known brands or institutions, often accompanied by deceptive login pages.

10:15:03.123456 IP user_ip.12345 > phishing_site_ip.80: GET /login.php
10:15:03.123457 IP phishing_site_ip.80 > user_ip.12345: Fake login page HTML

DNS Poisoning Attack#

DNS poisoning attacks manipulate DNS (Domain Name System) responses to redirect users to malicious websites, often for phishing or malware distribution.

Suspicious DNS traffic can be spotted in tcpdump captures by looking for discrepancies between DNS query requests and responses. Unexpected or unauthorized IP addresses in DNS responses may indicate poisoning.

10:25:08.987654 IP user_ip.12345 > DNS_server_ip.53: DNS query for trusted_site.com

Cross-Site Scripting (XSS) Attack#

XSS attacks involve injecting malicious scripts into web applications, which are then executed by unsuspecting users’ browsers. These scripts can steal cookies, session data, or sensitive information.

Tcpdump captures may reveal suspicious JavaScript or code injections in HTTP requests or responses. Look for payloads that attempt to execute scripts or load external resources from untrusted sources.

10:58:45.987654 IP user_ip.12345 > target_ip.80: GET /vulnerable_page.php?input=<script>alert('XSS')</script>

Ransomware Communication#

Ransomware attacks often involve communication between an infected host and a command and control (C2) server to exchange encryption keys and instructions.

Tcpdump captures may show unusual network traffic patterns, such as a sudden increase in traffic to specific IP addresses or domains that are indicative of ransomware communication.

10:12:30.987654 IP infected_host_ip > ransomware_server_ip: Encrypted communication

ARP Spoofing (ARP Cache Poisoning)#

ARP spoofing attacks manipulate ARP (Address Resolution Protocol) messages to redirect network traffic to an attacker’s device, allowing for eavesdropping or interception.

Look for ARP packets that indicate conflicting MAC addresses or frequent changes in ARP mappings for the same IP address, which may indicate ARP spoofing.

10:05:15.123456 ARP Request: Who has IP target_ip? Tell attacker_mac
10:05:15.123457 ARP Reply: target_ip is at attacker_mac

Botnet Activity#

Botnets are networks of compromised devices controlled by malicious actors. Tcpdump captures may reveal communication between infected devices and command and control servers, indicating botnet activity.

Observe traffic patterns where multiple devices communicate with a central IP address, especially if these communications include suspicious or malicious payloads.

10:22:58.987654 IP infected_device_1 > botnet_c2_server: Botnet communication
10:22:59.123456 IP infected_device_2 > botnet_c2_server: Botnet communication

Smurf Attack#

Smurf attacks exploit ICMP (Internet Control Message Protocol) to flood a target network with ICMP echo requests (pings) by spoofing the source IP address. This can lead to network congestion and denial of service.

Look for a significant increase in ICMP traffic, particularly ICMP echo requests (Type 8) with a spoofed source IP address.

10:08:12.987654 IP attacker_ip > broadcast_ip: ICMP echo request (ping) with spoofed source

SYN Flood Attack#

SYN flood attacks exploit the TCP handshake process by sending a large number of TCP SYN packets to overwhelm a target server, preventing legitimate connections.

Observe a high volume of incoming TCP SYN packets to a specific server or IP address. The server may respond with SYN-ACK packets, but the final ACK handshake may not be completed.

10:02:05.123456 IP source_ip.12345 > target_ip.80: SYN
10:02:05.123457 IP source_ip.12346 > target_ip.80: SYN
10:02:05.123458 IP source_ip.12345 > target_ip.80: SYN
10:02:05.123459 IP source_ip.12346 > target_ip.80: SYN
10:02:05.123460 IP source_ip.12345 > target_ip.80: SYN
10:02:05.123461 IP source_ip.12346 > target_ip.80: SYN

DNS Amplification Attack#

DNS amplification attacks involve sending a small DNS query to a DNS server with a spoofed source IP address, causing the server to respond with a larger DNS response to the victim’s IP, amplifying the attack traffic.

Look for unusual DNS query-response patterns with significantly larger responses than queries. These attacks can result in high DNS traffic.

10:32:20.987654 IP victim_ip > open_dns_server_ip: DNS query for example.com
10:32:20.987655 IP open_dns_server_ip > victim_ip: Large DNS response for example.com

Zero-Day Exploits#

Zero-day exploits target vulnerabilities in software or hardware that are not yet known to the vendor or the public, making them difficult to detect using known attack signatures.

Identifying zero-day exploits through network packet captures can be challenging. Look for patterns of unusual or unexpected traffic, sudden system crashes, or unexpected behavior in the network. Further investigation is often required to confirm a zero-day attack.

Final Words#

In the ever-evolving landscape of cybersecurity, staying one step ahead of network threats is imperative for organizations and individuals alike. The deployment of protocol analyzers in digital forensic investigations is a caluable step towards achieving this goal. These tools enable investigators to peer into the intricacies of network traffic, unveiling the tactics employed by malicious actors and providing critical insights for effective incident response.

As demonstrated through our exploration of common network attacks and their identification using protocol analyzer output, these tools serve as vital tools in the defense of digital assets. They empower investigators to detect patterns, anomalies, and the telltale signatures of attacks, thereby facilitating prompt and informed responses.