Alternate encoding such as hexadecimal representations is MOST often observed in which of the following forms of attack?

Smurf attacks are network-layer amplification DDoS attacks that abuse ICMP echo requests sent to broadcast addresses and do not involve alternate character encoding.

Rootkit exploits focus on gaining and maintaining privileged access at the OS or firmware level through system call hooking or binary replacement, not through encoding obfuscation of web input.

Denial of Service attacks overwhelm target resources with traffic or requests and do not rely on alternate encoding schemes as a primary attack vector.

In XSS attacks, threat actors use alternate encodings such as hexadecimal (e.g., %3Cscript%3E for <script>), Unicode, or HTML entity encoding to obfuscate malicious payloads and evade input sanitization filters. These encoded strings are injected into web applications where they are eventually decoded and executed by the victim's browser, making encoding a hallmark technique of XSS exploitation.