The regular expression provided in the question is designed to detect patterns that are typically found in XSS (Cross-Site Scripting) attacks. Here's a breakdown of the regex pattern:
* /((\%3C)|<) - This part of the pattern matches the encoded version of < which is %3C, or the symbol < itself. In HTML, this symbol denotes the start of a tag.
* ((\%69)|i|(\%49)) - This matches the encoded version of i which is %69, the lowercase i, or the encoded version of I which is %49.
* ((\%6D)|m|(\%4D)) - This matches the encoded version of m which is %6D, the lowercase m, or the encoded version of M which is %4D.
* ((\%67)|g|(\%47)) - This matches the encoded version of g which is %67, the lowercase g, or the encoded version of G which is %47.
* [^\n]+ - This part of the pattern matches one or more characters that are not a newline character.
* ((\%3E)|>) - This matches the encoded version of > which is %3E, or the symbol > itself, denoting the end of an HTML tag.
The combination of these patterns is looking for a string that resembles an HTML img tag, which is a common vector for XSS attacks. XSS attacks involve injecting malicious scripts into webpages viewed by other users, exploiting the trust a user has for a particular site. XSS attacks can occur when a web application uses unsanitized user input in the output it generates.
References: The EC-Council's Certified SOC Analyst (CSA) program covers the knowledge required to detect and analyze various types of cyber threats, including XSS attacks. The CSA program's curriculum includes understanding of IDS logs and the ability to interpret and respond to potential security events indicated by such logs. For further study and verification, please refer to the official EC-Council CSA study guides and course materials.

The /var/log/wtmp file in Linux systems is used to record all logins and logouts. The wtmp file is a binary file that can be read with tools like last, which can display the login history of all users or a specific user, as well as the times of system reboots and shutdowns. SOC analysts, like Chloe, would inspect this file to track user activities and investigate potential unauthorized access or other security incidents.
References: The EC-Council's Certified SOC Analyst (CSA) course provides extensive training and knowledge on SOC operations, including log management and correlation. The CSA certification emphasizes the importance of understanding various log files and their purposes within a Linux system as part of the SOC analyst's role12. For more detailed information, the EC-Council's official CSA study guides and resources should be consulted.