You want to carry out session hijacking on a remote server. The server and the client are communicating via TCP after a successful TCP three way handshake. The server has just received packet #120 from the client. The client has a receive window of 200 and the server has a receive window of 250.Within what range of sequence numbers should a packet, sent by the client fall in order to be accepted by the server?
Answer(s): B
Package number 120 have already been received by the server and the window is 250 packets, so any package number from 121 (next in sequence) to 371 (121+250).
How would you prevent session hijacking attacks?
Answer(s): D
Protection of a session needs to focus on the unique session identifier because it is the only thing that distinguishes users. If the session ID is compromised, attackers can impersonate other users on the system. The first thing is to ensure that the sequence of identification numbers issued by the session management system is unpredictable; otherwise, it's trivial to hijack another user's session. Having a large number of possible session IDs (meaning that they should be very long) means that there are a lot more permutations for an attacker to try.
Which of the following attacks takes best advantage of an existing authenticated connection?
Session hijacking is the act of taking control of a user session after successfully obtaining or generating an authentication session ID. Session hijacking involves an attacker using captured, brute forced or reverse-engineered session IDs to seize control of a legitimate user's Web application session while that session is still in progress.
After a client sends a connection request (SYN) packet to the server, the server will respond (SYN-ACK) with a sequence number of its choosing, which then must be acknowledge (ACK) by the client. This sequence number is predictable; the attack connects to a service first with its own IP address, records the sequence number chosen and then opens a second connection from a forget IP address. The attack doesn’t see the SYN-ACK (or any other packet) from the server, but can guess the correct responses. If the source IP Address is used for authentication, the attacker can use the one-side communication to break into the server.What attacks can you successfully launch against a server using the above technique?
Answer(s): A
The term Session Hijacking refers to the exploitation of a valid computer session - sometimes also called a session key - to gain unauthorised access to information or services in a computer system. In particular, it is used to refer to the theft of a magic cookie used to authenticate a user to a remote server. It has particular relevance to web developers, as the HTTP cookies used to maintain a session on many web sites can be easily stolen by an attacker using an intermediary computer or with access to the saved cookies on the victim's computer.
Sara is making use of Digest Authentication for her Web site. Why is this considered to be more secure than Basic authentication?
Digest access authentication is one of the agreed methods a web page can use to negotiate credentials with a web user (using the HTTP protocol). This method builds upon (and obsoletes) the basic authentication scheme, allowing user identity to be established without having to send a password in plaintext over the network.
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