{"id":936,"date":"2025-12-16T12:26:00","date_gmt":"2025-12-16T12:26:00","guid":{"rendered":"https:\/\/zombierollz.blog\/?p=936"},"modified":"2025-12-16T18:26:36","modified_gmt":"2025-12-16T18:26:36","slug":"aoc2025-day-13-yara-rules-yara-mean-one","status":"publish","type":"post","link":"https:\/\/zombierollz.blog\/?p=936","title":{"rendered":"AoC2025 – Day 13 YARA Rules – YARA mean one!"},"content":{"rendered":"\n

https:\/\/tryhackme.com\/room\/yara-aoc2025-q9w1e3y5u7
Created by: tryhackme, krotovolb
https:\/\/www.youtube.com\/watch?v=NAYtCSUHR8M is a great walkthrough video; he also gives a shoutout to regex 101: https:\/\/regex101.com\/, something that helped me in this room, and I bookmarked as well for future use cases!<\/p>\n\n\n\n

“When McSkidy went missing, there was chaos and uncertainty at The Best Festival Company (TBFC). However, even in her disappearance, McSkidy was trying to help the TBFC blue team. Taking a page out of the crisis communication process, McSkidy sent what looks like a bunch of images to the blue team from an anonymous location. These images looked like they were related to Easter preparations, but they contained a message sent by McSkidy. The crisis communication process outlines that a message might be sent through a folder of images containing hidden messages that can be decoded if you know the keyword. The blue team has to create a YARA rule that runs on the directory containing the images. The YARA rule must trigger on a keyword followed by a code word. After extracting all the code words in ascending order, the blue team will be able to decode the message.”<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

After reading the material, we are presented with our technical challenge: To make our own YARA rule. To the terminal we go! I made a file from nano called TBFC_Egg_Buster. The condition is this:<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n
\"\"<\/figure>\n\n\n\n

I added additional strings to what was already there. I’m not sure if this will mess with it, but we will find out. I was met with a syntax error! I ended up copying and pasting the rule without the ending bracket. Now that it’s fixed, I tried again.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n
\"\"<\/figure>\n\n\n\n
\"\"<\/figure>\n\n\n\n
\"\"<\/figure>\n\n\n\n
\"\"<\/figure>\n\n\n\n

“How many images contain the string TBFC?”

It will show duplicates, so if you count them with that in mind, it will be 5 images.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

“What regex would you use to match a string that begins with\u00a0TBFC:<\/code>\u00a0followed by one or more alphanumeric ASCII characters?”<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

“What is the message sent by McSkidy?” Copy and paste this into your Nano file and re-run it to obtain the message! It will be out of order, but we can figure that out!<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n
\"\"<\/figure>\n\n\n\n

Snippet highlights:<\/p>\n\n\n\n

\"\"<\/figure>\n","protected":false},"excerpt":{"rendered":"

https:\/\/tryhackme.com\/room\/yara-aoc2025-q9w1e3y5u7Created by: tryhackme, krotovolbhttps:\/\/www.youtube.com\/watch?v=NAYtCSUHR8M is a great walkthrough video; he also gives a shoutout to regex 101: https:\/\/regex101.com\/, something that helped me in this room, and I bookmarked as well for future use cases! “When McSkidy went missing, there was chaos and uncertainty at The Best Festival Company (TBFC). However, even in her disappearance, McSkidy […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-936","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"blocksy_meta":{"styles_descriptor":{"styles":{"desktop":"","tablet":"","mobile":""},"google_fonts":[],"version":8}},"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/zombierollz.blog\/index.php?rest_route=\/wp\/v2\/posts\/936","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/zombierollz.blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/zombierollz.blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/zombierollz.blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/zombierollz.blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=936"}],"version-history":[{"count":2,"href":"https:\/\/zombierollz.blog\/index.php?rest_route=\/wp\/v2\/posts\/936\/revisions"}],"predecessor-version":[{"id":951,"href":"https:\/\/zombierollz.blog\/index.php?rest_route=\/wp\/v2\/posts\/936\/revisions\/951"}],"wp:attachment":[{"href":"https:\/\/zombierollz.blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=936"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/zombierollz.blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=936"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/zombierollz.blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=936"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}