Bidirectional (Bidi) characters are special Unicode control characters that manage the direction in which text is displayed, especially for languages written right-to-left (like Arabic or Hebrew) alongside left-to-right languages. In cybersecurity, attackers may exploit Bidi characters to manipulate how source code or file names appear, potentially hiding malicious code or misleading users. This technique can be used in phishing attacks or to obfuscate malware, making detection more difficult. Awareness and detection of Bidi characters are important for secure coding and threat prevention.