GCFA · Question #15
Adam works as a Security Administrator for Umbrella Inc. He is responsible for securing all 15 servers of the company. To successfully accomplish the task, he enables the hardware and software…
The correct answer is C. Grabbed the banner. Sending 'HEAD / HTTP/1.0' via telnet is a classic banner-grabbing technique that retrieves HTTP response headers, revealing web server type, version, and OS information. This is a standard footprinting step in penetration testing.
Question
Adam works as a Security Administrator for Umbrella Inc. He is responsible for securing all 15 servers of the company. To successfully accomplish the task, he enables the hardware and software firewalls and disables all unnecessary services on all the servers. Sales manager of the company asks Adam to run emulation software on one of the servers that requires the telnet service to function properly. Adam is concerned about the security of the server, as telnet can be a very large security risk in an organization. Adam decides to perform some footprinting, scanning, and penetration testing on the server to checkon the server to check the security. Adam telnets into the server and writes the following command:
HEAD / HTTP/1.0 After pressing enter twice, Adam gets the following results:
Which of the following tasks has Adam just accomplished?
Exhibit
Options
- APoisoned the local DNS cache of the server.
- BSubmitted a remote command to crash the server.
- CGrabbed the banner.
- DDownloaded a file to his local computer.
How the community answered
(27 responses)- A4% (1)
- B4% (1)
- C81% (22)
- D11% (3)
Why each option
Sending 'HEAD / HTTP/1.0' via telnet is a classic banner-grabbing technique that retrieves HTTP response headers, revealing web server type, version, and OS information. This is a standard footprinting step in penetration testing.
DNS cache poisoning requires sending crafted DNS responses to corrupt a resolver's cache, which is unrelated to sending an HTTP HEAD request via telnet.
A standard HTTP HEAD request is a benign, RFC-compliant method that retrieves headers only and does not contain any payload capable of crashing a server.
The HTTP HEAD method instructs the server to return only the response headers, not the body, for the requested resource. When sent manually via telnet, the server responds with headers such as 'Server:', 'Date:', and 'Content-Type:', which reveal the web server software and version - this is called banner grabbing. It is a passive reconnaissance technique used during the information-gathering phase of a penetration test to fingerprint the target server without triggering intrusive alerts.
The HEAD method explicitly instructs the server NOT to return a message body, so no file content is transmitted or downloaded to the client.
Concept tested: HTTP banner grabbing via telnet for server fingerprinting
Source: https://owasp.org/www-project-web-security-testing-guide/latest/4-Web_Application_Security_Testing/01-Information_Gathering/02-Fingerprint_Web_Server
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