In OS fingerprinting, which attributes of a response are commonly analyzed to guess the target OS?

In OS fingerprinting, which attributes of a response are commonly analyzed to guess the target OS?

• A. IP address and DNS records
• B. Port numbers and service banners
• C. Time To Live (TTL) and window size
• D. MAC address and vendor ID

Answer: (C)

OS fingerprinting hinges on how a target’s TCP/IP stack responds to crafted probes, with certain response attributes serving as telltale signs of the operating system. The most informative are the Time To Live (TTL) value and the TCP window size. TTL is set by the sending OS and each hop reduces it by one; different OS families tend to use characteristic initial TTL values (for example 64, 128, or 255). By observing the TTL in replies, you can estimate how many hops were traversed and which OS family is likely. The TCP window size reveals how the sender’s stack configures flow control for connections; default window sizes and subsequent scaling behavior vary across OS implementations, producing distinctive fingerprints in responses to probes. When you combine TTL and window size, you get a reliable signal about the target’s stack. Other options don’t map as directly to the OS. IP address and DNS records show where a host is or what name it uses, not what it’s running. Ports and service banners indicate what services are active, but many OSes can run the same services. MAC address and vendor ID identify the network interface hardware and are typically visible only within the local network; they don’t reliably indicate the operating system on distant hosts.

OS fingerprinting hinges on how a target’s TCP/IP stack responds to crafted probes, with certain response attributes serving as telltale signs of the operating system. The most informative are the Time To Live (TTL) value and the TCP window size. TTL is set by the sending OS and each hop reduces it by one; different OS families tend to use characteristic initial TTL values (for example 64, 128, or 255). By observing the TTL in replies, you can estimate how many hops were traversed and which OS family is likely. The TCP window size reveals how the sender’s stack configures flow control for connections; default window sizes and subsequent scaling behavior vary across OS implementations, producing distinctive fingerprints in responses to probes. When you combine TTL and window size, you get a reliable signal about the target’s stack.

Other options don’t map as directly to the OS. IP address and DNS records show where a host is or what name it uses, not what it’s running. Ports and service banners indicate what services are active, but many OSes can run the same services. MAC address and vendor ID identify the network interface hardware and are typically visible only within the local network; they don’t reliably indicate the operating system on distant hosts.