A forensic analyst is conducting an investigation on a compromised server. The first step that the analyst should do to preserve evidence is to back up all log files and audit trails. This will ensure that the analyst has a copy of the original data that can be used for analysis and verification. Backing up the log files and audit trails will also prevent any tampering or modification of the evidence by the attacker or other parties. The other options are not the first steps or may alter or destroy the evidence. Reference: CompTIA Cybersecurity Analyst (CySA+) Certification Exam Objectives (CS0-002), page 16; https://www.nist.gov/publications/guide-collection-and-preservation-digital-evidence

Threat hunting is a proactive process of searching for signs of malicious activity or compromise within a system or network, by using hypotheses, indicators of compromise, and analytical tools. Threat hunting can help improve detection capabilities by identifying unknown threats, uncovering gaps in security controls, and providing insights for remediation and prevention. Vulnerability scanning (A) is a reactive process of scanning systems or networks for known vulnerabilities or weaknesses that can be exploited by attackers. It can help identify and prioritize vulnerabilities, but not proactively hunt for threats. Red teaming is a simulated attack on a system or network by a group of ethical hackers who act as adversaries and try to breach security controls. It can help test the effectiveness of security defenses and response capabilities, but not proactively hunt for threats. Penetration testing (D) is similar to red teaming, but with a more defined scope and objective. It can help evaluate the security of a system or network by simulating real-world attacks and exploiting vulnerabilities, but not proactively hunt for threats.

Port 22 is the default port for Secure Shell (SSH), which is a protocol that allows remote access and administration of a server. If the server is dedicated to one function (web server) and unneeded services are disabled, then port 22 should be closed, because SSH is not necessary for a web server and could pose a security risk if exploited. Port 80, port 443, and port 1433 are ports that are needed for a web server, because they are used for HTTP, HTTPS, and SQL Server respectively. Reference: https://www.ssh.com/ssh/port

DKIM, or DomainKeys Identified Mail, is an email authentication method that uses a digital signature to let the receiver of an email know that the message was sent and authorized by the owner of a domain1 DKIM helps prevent phishing emails that spoof or impersonate other domains by verifying the identity and integrity of the sender. DKIM works by adding a DKIM signature header to each outgoing email message, which contains a hash value of selected parts of the message and the domain name of the sender. The sender's domain also publishes a public key in its DNS records, which can be used by the receiver to decrypt the DKIM signature and compare it with its own hash value of the message. If they match, it means that the message was not altered in transit and that it came from the claimed domain.

Credentialed scanning is a method of vulnerability scanning that uses valid user credentials to access the target systems and perform a more thorough and accurate assessment of their security posture. Credentialed scanning can help to reduce the number of false positives by allowing the scanner to access more information and resources on the systems, such as configuration files, registry keys, installed software, patches, and permissions .