Query: adversary uses HTML Smuggling
Matching passage: T1027.006 HTML Smuggling. Tactics: stealth. Description: Adversaries may smuggle data and files past content filters by hiding malicious payloads inside of seemingly benign HTML files. HTML documents can store large binary objects known as JavaScript Blobs (immutable data that represents raw bytes) that can later be constructed into file-like objects. Data may also be stored in Data URLs, which enable embedding media type or MIME files inline of HTML documents. HTML5 also introduced a download attribute that may be used to initiate file downloads.(Citation: HTML Smuggling Menlo Security 2020)(Citation: Outlflank HTML Smuggling 2018) Adversaries may deliver payloads to victims that bypass security controls through HTML Smuggling by abusing JavaScript Blobs and/or HTML5 download attributes. Security controls such as web content filters may not identify smuggled malicious files inside of HTML/JS files, as the content may be based on typically benign MIME types such as <code>text/plain</code> and/or <code>text/html</code>. Malicious files or data can be obfuscated and hidden inside of HTML files through Data URLs and/or JavaScript Blobs and can be deobfuscated when they reach the victim (i.e. [Deobfuscate/Decode Files or Information](https://attack.mitre.org/techniques/T1140)), potentially bypassing content filters. For example, JavaScript Blobs can be abused to dynamically generate malicious files in the victim machine and may be dropped to disk by abusing JavaScript functions such as <code>msSaveBlob</code>.(Citation: HTML Smuggling Menlo Security 2020)(Citation: MSTIC NOBELIUM May 2021)(Citation: Outlflank HTML Smuggling 2018)(Citation: nccgroup Smuggling HTA 2017)
Near-miss passage: T1027.015 Compression. Tactics: stealth. Description: Adversaries may use compression to obfuscate their payloads or files. Compressed file formats such as ZIP, gzip, 7z, and RAR can compress and archive multiple files together to make it easier and faster to transfer files. In addition to compressing files, adversaries may also compress shellcode directly - for example, in order to store it in a Windows Registry key (i.e., [Fileless Storage](https://attack.mitre.org/techniques/T1027/011)).(Citation: Trustwave Pillowmint June 2020) In order to further evade detection, adversaries may combine multiple ZIP files into one archive. This process of concatenation creates an archive that appears to be a single archive but in fact contains the central directories of the embedded archives. Some ZIP readers, such as 7zip, may not be able to identify concatenated ZIP files and miss the presence of the malicious payload.(Citation: Perception Point) File archives may be sent as one [Spearphishing Attachment](https://attack.mitre.org/techniques/T1566/001) through email. Adversaries have sent malicious payloads as archived files to encourage the user to interact with and extract the malicious payload onto their system (i.e., [Malicious File](https://attack.mitre.org/techniques/T1204/002)).(Citation: NTT Security Flagpro new December 2021) However, some file compression tools, such as 7zip, can be used to produce self-extracting archives. Adversaries may send self-extracting archives to hide the functionality of their payload and launch it without requiring multiple actions from the user.(Citation: The Hacker News) [Compression](https://attack.mitre.org/techniques/T1027/015) may be used in combination with [Encrypted/Encoded File](https://attack.mitre.org/techniques/T1027/013) where compressed files are encrypted and password-protected.