CEH Practice Question: Malware, Social Engineering and Network Attacks
Which THREE of the following are indicators of a slowloris DDoS attack?
⚠ Common exam trap
The trap here is that candidates often associate DDoS attacks with high traffic volume, but Slowloris is a low-and-slow attack that uses normal traffic volume with persistent, incomplete connections, so they may incorrectly select high-volume options like A or E.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Normal traffic volume but connections remain open for a long time
B is correct because a Slowloris DDoS attack works by opening many connections to a target web server and keeping them open for as long as possible, sending partial HTTP requests to tie up server resources. This results in normal traffic volume but with connections that remain open for extended periods, preventing legitimate users from connecting.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
ICMP echo replies from random IPs
Why it's wrong here
ICMP (Internet Control Message Protocol) echo replies from various, often spoofed, IP addresses are characteristic of a Smurf attack, a type of DDoS that amplifies traffic by sending ICMP echo requests to a broadcast address. Slowloris, in contrast, is an application-layer denial-of-service attack that exclusively targets HTTP servers using TCP connections. It does not involve ICMP at any stage of its operation, making this indicator irrelevant to a Slowloris attack.
- ✓
Normal traffic volume but connections remain open for a long time
Why this is correct
Slowloris is a low-bandwidth attack that does not generate a high volume of data packets. Instead, it exploits the server's connection handling by opening numerous legitimate-looking HTTP connections and then keeping them alive for extended durations. This is achieved by sending partial HTTP requests and periodically sending additional, non-terminating HTTP headers, preventing the server from timing out the connection and freeing up resources. The prolonged open state of these connections, despite minimal data transfer, exhausts the server's available connection pool.
- ✓
Many half-open HTTP connections
Why this is correct
A key indicator of a Slowloris attack is the presence of numerous "half-open" HTTP connections on the target server. Slowloris initiates a standard TCP connection, but then it deliberately sends only a partial HTTP request header, such as "GET / HTTP/1.1\r\nHost: example.com\r\nUser-Agent: Mozilla/4.0\r\n". It then pauses, sending only small, non-terminating header fragments (e.g., "X-a: b\r\n") at regular intervals. This prevents the server from considering the request complete or timing out the connection, effectively tying up server resources in a waiting state.
- ✓
Server logs showing incomplete HTTP requests
Why this is correct
Server logs are a critical forensic tool, and in the context of a Slowloris attack, they will reveal a high number of entries for HTTP requests that never reached completion. Because Slowloris sends only partial HTTP headers and never the final double carriage return and newline (\r\n\r\n) that signals the end of the header section, the server's HTTP parser cannot finalize the request. These incomplete requests remain in a pending state, consuming server memory and CPU cycles, and are often logged as aborted or incomplete transactions, distinct from typical client disconnections.
- ✗
High volume of UDP packets
Why it's wrong here
A high volume of UDP (User Datagram Protocol) packets is not an indicator of a Slowloris attack. Slowloris is an application-layer attack specifically designed to target HTTP servers, which operate over TCP (Transmission Control Protocol) on port 80 or 443. UDP is a connectionless protocol primarily used for services like DNS, NTP, or streaming media, and is not utilized by Slowloris in any capacity. A high volume of UDP traffic would suggest a different type of DDoS attack, such as a DNS amplification or NTP amplification attack.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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