ECCouncil Updated 312-50v13 Exam Questions and Answers by gruffydd

In the CEH Denial-of-Service and Network Attacks coverage, a SYN flood is a classic TCP-based DoS technique that exploits the TCP connection establishment process. In a normal handshake, the client sends SYN, the server replies SYN/ACK, and the client completes with ACK. A SYN flood deliberately sends a high volume of SYN packets (often spoofed) but never completes the final ACK. As CEH describes, this leaves the server holding many half-open connections in SYN_RECEIVED, consuming memory and connection table resources (backlog queue). When the backlog fills, legitimate clients cannot establish connections, degrading availability.

The indicators in your scenario align exactly with CEH’s SYN flood fingerprints: incomplete handshakes and accumulation of half-open connections. The goal is resource exhaustion at the connection-management layer rather than bandwidth saturation.

Option B (Ping of Death) involves malformed/oversized ICMP packets and does not match SYN_RECEIVED behavior. Option C (UDP flood) targets UDP services/ports and creates different symptoms (high UDP traffic, ICMP unreachable messages, service degradation) without half-open TCP states. Option D (Smurf) is ICMP-based amplification via broadcast addresses—again unrelated to incomplete TCP handshakes.

CEH also notes mitigations such as SYN cookies, increasing backlog, reducing SYN-RECEIVED timers, rate limiting, and upstream filtering—further reinforcing that the described event is a SYN flood.

This question is about web link enumeration using Linux CLI tools — a common initial step during information gathering in penetration testing, covered in CEH v13 Module 02: Footprinting and Reconnaissance.

Objective:

Extract all hyperlinks (i.e., ) from the homepage of a target site to collect subpages, links, or external URLs.

Let’s analyze each component of Option B:

=

=

curl -s https://site.com | grep '

curl -s https://site.com: Silently fetches the HTML source of the main page.

grep '

grep "site.com": Further filters those that point to site.com.

cut -d "v" -f 2: Cuts the line based on the delimiter v to isolate part of the URL — though not perfect, it attempts to extract the visible link.

While not perfectly formed (due to slightly inconsistent quote usage), Option B demonstrates the correct logic chain for web link enumeration using pipes in Linux: fetching, filtering, and extracting.

Why Other Options Are Incorrect:

A. dirb https://site.com | grep "site"

❌ dirb is used for brute-forcing directories, not grabbing links from HTML.

C. wget https://site.com | grep "

❌ Incorrect. wget will download the entire content (including binary files by default), and piping it directly to grep without -O - or -q -O - makes it ineffective.

D. wget https://site.com | cut -d "http"

❌ Incorrect. Syntax error (cut -d"http" is invalid without correct delimiter formatting), and again wget needs to be directed to stdout using -O -.

Corrected Optimal Syntax for Real-World Use:

bash

CopyEdit

curl -s https://site.com | grep -oP 'href="\Khttp[^"]+' | grep "site.com"

This uses -oP with Perl-compatible regex to extract only URLs and is a method recommended in CEH iLabs and demonstrations.

Reference from CEH v13 Study Materials:

Module 02 – Footprinting and Reconnaissance, Section: Website Footprinting and Web Crawling

CEH iLabs – Website Information Gathering Lab

CEH Engage Range: Passive and Active Footprinting Phase – Linux Scripting Tasks

We have various articles already in our documentation for setting up SNMPv2 trap handling in Opsview, but SNMPv3 traps are a whole new ballgame. They can be quite confusing and complicated to set up the first time you go through the process, but when you understand what is going on, everything should make more sense.

SNMP has gone through several revisions to improve performance and security (version 1, 2c and 3). By default, it is a UDP port based protocol where communication is based on a ‘fire and forget’ methodology in which network packets are sent to another device, but there is no check for receipt of that packet (versus TCP port when a network packet must be acknowledged by the other end of the communication link). 

There are two modes of operation with SNMP – get requests (or polling) where one device requests information from an SNMP enabled device on a regular basis (normally using UDP port 161), and traps where the SNMP enabled device sends a message to another device when an event occurs (normally using UDP port 162). The latter includes instances such as someone logging on, the device powering up or down, or a wide variety of other problems that would need this type of investigation.

This blog covers SNMPv3 traps, as polling and version 2c traps are covered elsewhere in our documentation.

SNMP traps

Since SNMP is primarily a UDP port based system, traps may be ‘lost’ when sending between devices; the sending device does not wait to see if the receiver got the trap. This means if the configuration on the sending device is wrong (using the wrong receiver IP address or port) or the receiver isn’t listening for traps or rejecting them out of hand due to misconfiguration, the sender will never know.

The SNMP v2c specification introduced the idea of splitting traps into two types; the original ‘hope it gets there’ trap and the newer ‘INFORM’ traps. Upon receipt of an INFORM, the receiver must send an acknowledgement back. If the sender doesn’t get the acknowledgement back, then it knows there is an existing problem and can log it for sysadmins to find when they interrogate the device.

In CEH v13 Module 07: Evading IDS, Firewalls, and Honeypots, various honeypot detection techniques are discussed. One such method is time-based TCP fingerprinting, which is effective against Honeyd-based honeypots.

Honeyd Honeypots:

Lightweight, low-interaction honeypots.

Often respond with inconsistent or delayed TCP timestamps.

Can be fingerprinted by comparing round-trip time and TTL values to real systems.

Option Clarification:

A. VMware detection: Uses CPU/BIOS identifiers and MAC address patterns.

B. Honeyd detection: Correct — uses time-based TCP fingerprinting.

C. Snort_inline: A network-based IPS, not the context here.

D. Sebek: Used to monitor user-level activity, not related to TCP response timing.