GCIH Network and Log Investigations — 15 Questions

Question 1

Refer to the exhibit. An analyst observes this log entry in the web server access logs. What type of attack is likely being attempted?

Accepted Answer

SQL Injection. The inclusion of the single quote and double hyphen (--) in the query parameter is a classic signature for SQL injection. Attackers use the quote to break out of the string context and the dashes to comment out the remainder of the legitimate SQL query. Identifying these patterns in logs is vital for detecting application-layer exploitation attempts that bypass traditional perimeter firewalls.

Answer

Cross-Site Scripting (XSS)

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Directory Traversal

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Buffer Overflow

Question 2

A responder is analyzing a compromised Linux host and suspects the attacker modified a persistent startup file to maintain access. Which file should be checked to identify malicious commands executing upon system boot?

Accepted Answer

~/.bashrc. Persistence mechanisms are a primary goal for attackers. On Linux, attackers often target shell profile files or systemd services to ensure their backdoors run automatically. Checking /etc/crontab or specific user profile files is fundamental to incident investigation. Identifying these modifications allows responders to not only remove the malicious persistence but also to understand the scope and duration of the attacker's presence on the system.

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/etc/shadow

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/var/log/syslog

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/proc/net/dev

Question 3

During a forensic analysis, you identify that an attacker used a 'Pass-the-Hash' (PtH) attack. Which Windows log event ID is most indicative of this authentication activity occurring on a target system?

Accepted Answer

Event ID 4624 (Logon Type 3). Pass-the-Hash attacks allow an attacker to authenticate without the original plaintext password. In Windows, this manifests as a network logon event using NTLM authentication. Monitoring for logon types, specifically Type 3, is vital for identifying these lateral movement attempts. Incident responders must distinguish between legitimate network service authentication and malicious PtH activity to effectively scope the breach and identify compromised accounts.

Answer

Event ID 4625 (Logon Type 2)

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Event ID 4688

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Event ID 4720

Question 4

Refer to the exhibit. A firewall policy is implemented as shown. If a packet arrives from 10.5.5.5 destined for 192.168.1.10, what will be the result?

Accepted Answer

The packet will be blocked.. The source IP 10.5.5.5 falls within the 10.0.0.0/8 CIDR range (covering 10.0.0.0 to 10.255.255.255). The destination 192.168.1.10 is within the 192.168.1.0/24 range (covering 192.168.1.0 to 192.168.1.255). Because both match the policy parameters and the action is 'block', the packet will be dropped. Understanding CIDR notation is essential for correctly auditing network security policies during incident response investigations.

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The packet will be allowed.

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The packet will be ignored.

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The packet will be routed to the DMZ.

Question 5

Which THREE log sources are most critical for reconstructing an attacker's movement across an Active Directory environment after they gain initial domain user access?

Accepted Answer

Domain Controller Security Event Logs. Active Directory logs provide the audit trail necessary for tracking lateral movement. Security event logs capture authentication, process creation, and service modifications. By correlating these, investigators can map the attacker's trajectory. If logs are missing, the ability to determine the extent of a compromise is severely hampered, making the integrity of these three log sources paramount for incident responders working in Windows-based enterprise environments.

Answer

DHCP Lease Logs

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Printer Spooler Logs

Question 6

When performing memory forensics, which artifact is the most reliable for identifying the parent-child relationship of suspicious processes?

Accepted Answer

The EPROCESS block. The EPROCESS structure in the Windows kernel maintains a list of processes and their parent process IDs. Forensic tools like Volatility parse these structures to visualize the process tree. This is essential for detecting 'process hollowing' or 'injection' where a malicious process is spawned by a legitimate one (like explorer.exe or services.exe), allowing investigators to reconstruct the exact execution chain used by an attacker.

Answer

System Prefetch files

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MFT (Master File Table)

Answer

Windows Event Logs

Question 7

During an investigation involving a compromised Linux server, an incident responder suspects an attacker installed a user-mode rootkit by replacing standard system binaries. The responder runs the 'rpm -Va' command to verify installed packages against the RPM database. Which specific finding from this verification output provides definitive cryptographic proof that the '/bin/netstat' binary has been modified?

Accepted Answer

A leading '5' indicator confirming that the cryptographic MD5 digest of the file does not match the RPM database record.. The rpm verification command checks installed files against the package database's cryptographic checksums and metadata. A digest or MD5 mismatch denoted by the '5' attribute flag indicates that the file contents on disk differ from the official package manifest, proving tampering occurred despite potential file timestamp manipulation.

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A leading 'S' indicator showing that the file size has changed significantly compared to the original installation manifest.

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A leading 'M' indicator demonstrating that the permission bits and file mode have been altered to grant world-writable access.

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A leading 'T' indicator showing that the file modification timestamp was altered to conceal the exact time of the replacement.

Question 8

A security analyst is reviewing logs from a Linux web server and notices the following entry in /var/log/auth.log: 'sshd[1234]: Accepted password for root from 192.168.1.100 port 54321 ssh2'. Shortly after, the same IP appears in /var/log/apache2/access.log with a POST request to /admin/upload.php that returns a 200 status code. The server hosts a public e-commerce site. Which of the following is the MOST likely explanation for these log entries?

Accepted Answer

An attacker used stolen credentials to log in via SSH and then uploaded a malicious file through the web application.. The correct answer is that an attacker used stolen credentials to log in via SSH and then uploaded a malicious file. The logs show a successful SSH login as root from an external IP, followed by a POST to an admin upload script. This indicates the attacker had valid credentials and then leveraged the web application to upload a payload. The absence of failed login attempts supports credential use rather than brute force. This is a classic attack chain.

Answer

A legitimate administrator logged in via SSH and then uploaded a file through the web interface.

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An attacker exploited a vulnerability in the web application to gain SSH access.

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An attacker successfully brute-forced the root password and then uploaded a web shell.

Question 9

During an investigation of a compromised Linux server, an incident responder needs to determine which user account was used to establish an SSH session that originated from an external IP address. Which log file should the responder examine to find the username associated with the successful login?

Accepted Answer

/var/log/auth.log. On Debian-based Linux systems, authentication events including SSH logins are recorded in /var/log/auth.log. This file contains the username, source IP, and timestamp for successful logins. By examining auth.log, the responder can directly identify the account used from the external IP. Other logs either lack authentication details or are specific to other distributions.

Answer

/var/log/syslog

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/var/log/secure

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/var/log/lastlog

Question 10

An incident responder is reviewing firewall logs and notices a series of denied inbound connections from various external IP addresses to TCP port 3389 on a public-facing server. What is the most likely explanation for this activity?

Accepted Answer

The server is being scanned for open RDP ports by automated tools.. The denied inbound connections to port 3389 from multiple external IPs indicate that the server is being scanned for open RDP ports. Port scanning is a common reconnaissance technique used by attackers to identify potential entry points. Since the firewall is blocking the connections, the RDP service is not exposed, but the scan activity itself is noteworthy. This is not a brute-force attack because the connections are denied before reaching the service, and it is not C2 traffic because the direction and port are inconsistent with typical botnet communication.

Answer

The server is experiencing a brute-force attack against RDP.

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The server is part of a botnet and is receiving commands from a C2 server.

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A misconfigured application is repeatedly attempting to connect to the server.

Question 11

An incident responder is investigating a suspected compromise of a Windows workstation. The responder has collected volatile data and needs to identify evidence of persistence mechanisms. Which two artifacts should the responder examine to find programs configured to run automatically at startup? (Choose two.)

Accepted Answer

Registry keys under HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run. Persistence mechanisms on Windows often include registry Run keys and Startup folders. These locations automatically execute programs when a user logs in. Examining them reveals unauthorized additions. While Scheduled Tasks can also provide persistence, they are trigger-based and not exclusively startup programs. The two most direct artifacts for auto-start programs are the Run keys and Startup folders.

Answer

Windows Prefetch files

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Event logs in the Security log

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Scheduled Tasks in Task Scheduler

Question 12

An incident responder notices a spike in outbound traffic on port 443 originating from a server that normally only communicates with a local database. Which tool is most effective for identifying the specific process responsible for this anomalous network activity?

Accepted Answer

netstat -ano. Identifying the link between network sockets and the system process is critical during incident handling. Netstat or ss utilities, specifically when used with process identification flags, allow responders to map external traffic to local binaries. This visibility is essential for distinguishing between legitimate service communication and unauthorized exfiltration or command-and-control beacons, enabling the responder to terminate malicious processes and isolate affected infrastructure quickly.

Answer

tcpdump -i eth0

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nmap -sV target

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ifconfig -a

Question 13

An analyst is investigating potential data exfiltration via DNS tunneling. Which TWO of the following indicators would most strongly suggest this activity is occurring?

Accepted Answer

A sudden increase in DNS TXT record requests. DNS tunneling uses DNS queries to encapsulate non-DNS traffic, bypassing standard firewalls. Detecting this requires looking for abnormal patterns in traffic volume and request frequency. By identifying unusually long subdomains or high volumes of TXT/NULL record types, analysts can pinpoint covert channels. This is critical for detecting C2 traffic that hides in plain sight within common, often permitted, network protocols.

Answer

High volumes of HTTP GET requests to internal IPs

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Frequent ICMP echo requests from the perimeter

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TCP SYN floods targeting the local gateway

Question 14

Which of the following best describes the purpose of 'flow data' (like NetFlow) during an incident investigation?

Accepted Answer

To analyze the volume, source, and destination of network traffic.. Flow data provides a high-level summary of network communications, including source, destination, ports, and duration. Unlike full packet capture, which is resource-intensive, flow data is lightweight and allows for long-term retention. It is invaluable for reconstructing an attacker's movement across the network and identifying patterns of communication, such as beaconing to C2 servers, even when specific payload contents are not available.

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To capture the full payload content of every packet.

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To provide a record of who accessed which specific file.

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To perform real-time decryption of SSL/TLS traffic.

Question 15

You are analyzing a PCAP and notice a large number of packets with the 'RST' flag set. What is the most likely cause for this behavior in an incident context?

Accepted Answer

Port scanning activity.. The TCP RST (Reset) flag is used to abruptly terminate a connection. A surge of these packets can indicate an active port scan, a misconfigured firewall rejecting unauthorized traffic, or an attacker attempting to clear out half-open connections. Understanding TCP state transitions is fundamental to identifying network scanning or denial-of-service attempts during the investigation of anomalous traffic patterns in packet captures.

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Successful data transfer.

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Normal encrypted session renegotiation.

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DNS zone transfer.