Low-Level

EtherLeak is an ICMP information disclosure class that resurfaces across vendors and decades — same root cause, different hardware. IP stacks that trust IP_Total_Length over actual frame length expose NIC DMA ring buffer contents via ICMP Echo. Combined with TTL=0, extraction runs at 1,800 bytes/second with zero IDS alerts, zero firewall logs. Covers full mechanism, threshold math, Suricata detection rules, and Scapy PoC.

Fixed-interval C2 beacons produce detectable periodic patterns in SOC traffic baselines and behavioral analysis engines. LCG jitter breaks this: rdtsc reads the CPU Time Stamp Counter for hardware entropy, imul+add applies the Numerical Recipes LCG scramble (X = 1664525X + 1013904223 mod 2^32), div maps the result to [100ms, 1000ms), sys_nanosleep (syscall 35) executes the delay. Result: uniform random inter-beacon intervals with 2^32 period, zero external dependencies, full register preservation, pure x64 Assembly.

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.

Every HTTP server abstraction collapses to the same syscall chain: socket → bind → listen → accept → read → sendfile → close. In pure x86_64 Assembly, each step is explicit: bswap converts port to network byte order, SCASB/LODSB scans the GET request path byte-by-byte for ../ traversal sequences, sys_fstat retrieves exact file size for sys_sendfile, sys_sendfile(40) transfers file data directly from disk to NIC via kernel space — zero user-space copy, zero libc, zero external libraries. Full source on GitHub.