When it comes to packaging malware, the file format of choice remains Microsoft Word or Excel, but a recent attack using a PDF file to lure in victims caught the attention of researchers.
The campaign — observed by HP Wolf Security — sent the malicious PDF as an email attachment. Once opened, it used a variety of tactics to evade detection, embed malicious files, load remote exploits, and shellcode encryption, according to the researchers.
"Embedding files, loading remotely hosted exploits, and encrypting shellcode are just three techniques attackers use to run malware under the radar," the HP Wolf team reported on the malicious PDF attack in a recent blog post. "The exploited vulnerability in this campaign (CVE-2017-11882) is over four years old, yet continues being used, suggesting the exploit remains effective for attackers."