Shellcode

Uncompressed C2 payloads have two problems: size triggers bandwidth anomalies, and high-entropy raw shellcode scores above 7.5 on entropy analysis tools. VESQER addresses both: DPCM computes per-byte deltas (reducing entropy by exploiting local correlation), RLE collapses repeated delta values (reducing size on structured shellcode). Pure x64 Assembly, zero libc, zero dependencies. Complete implementation walkthrough: delta computation, run-length encoding loop, decode stub design, and measured compression ratios on real C2 payloads.

Standard Assembly code with absolute addresses breaks under ASLR — fixed addresses become invalid at runtime. PIC solves this via RIP-relative addressing: all memory references computed as offsets from the current instruction pointer. The Stack Anchor technique carves a 32KB R/W region (sub rsp,0x8000 + and rsp,-16 + mov rbp,rsp), providing writable storage without .data or .bss sections. Read-only templates in .text are copied to the stack via rep movsb for runtime modification. Result: a single position-independent code block deployable anywhere in memory — standard for shellcode, injection payloads, and fileless implants.

Implementing a reverse shell in pure x64 Assembly exposes the raw POSIX syscall sequence: socket() creates the TCP FD, connect() establishes the outbound connection, dup2() iterates 2→1→0 to redirect all three standard streams to the socket, execve() spawns /bin/sh which inherits the redirected FDs. PIC Stack Anchor (sub rsp,0x8000 + and rsp,-16 + mov rbp,rsp) enables ASLR-safe deployment — no absolute addresses, no .data/.bss, sockaddr_in struct copied from .text to writable stack via rep movsb. Zero libc, zero external dependencies.