image (as in the EURion constellation). In such a case, the technique of hiding the message (here, the watermark) must be robust to prevent tampering. However, digital watermarking sometimes requires a brittle watermark, which can be modified easily, to check whether the image has been tampered with. That is the key difference between steganography and digital watermarking. Alleged use by intelligence services In 2010, the Federal Bureau of Investigation alleged that the Russian foreign intelligence service uses customized steganography software for embedding encrypted text messages inside image files for certain communications with "illegal agents" (agents without diplomatic cover) stationed abroad. On April 23, 2019 the U.S. Department of Justice unsealed an indictment charging Xiaoqing Zheng, a Chinese businessman and former Principal Engineer at General Electric, with 14 counts of conspiring to steal intellectual property and trade secrets from General Electric. Zheng had allegedly used steganography to exfiltrate 20,000 documents from General Electric to Tianyi Aviation Technology Co. in Nanjing, China, a company the FBI accused him of starting with backing from the Chinese government. Distributed steganography There are distributed steganography methods, including methodologies that distribute the payload through multiple carrier files in diverse locations to make detection more difficult. For example, by cryptographer William Easttom (Chuck Easttom). Online challenge The puzzles that are presented by Cicada 3301 incorporate steganography with cryptography and other solving techniques since 2012. Puzzles involving steganography have also been featured in other alternate reality games. The communications of The May Day mystery incorporate steganography and other solving techniques since 1981. Computer malware It is possible to steganographically hide computer malware into digital images, videos, audio and various other files in order to evade detection by antivirus software. This type of malware is called stegomalware. It can be activated by external code, which can be malicious or even non-malicious if some vulnerability in the software reading the file is exploited. Stegomalware can be removed from certain files without knowing whether they contain stegomalware or not. This is done through content disarm and reconstruction (CDR) software, and it involves reprocessing the entire file or removing parts from it. Actually detecting stegomalware in a file can be difficult and may involve testing the file behaviour in virtual environments or deep learning analysis of the file. Stegoanalysis Stegoanalytical algorithms Stegoanalytical algorithms can be cataloged in different ways, highlighting: according to the available information and according to the purpose sought. According