2.3.1.2 some security measures to overcomeAbout user: recommends that users must know to protect yourself is to not click on the link of unknown origin or from unidentified persons in order to avoid the situation like the above example. recommends users should use exit your browser or leave the server deletes all of the files stored in the cache as a Cookie file, save the Session ID or other user information.About the server: Not allow login with a Session ID of available sessions that are created by the server. associated Session ID with the authentication information is encrypted with SSL of the user to set the expiration time for the Session, prevent Attacker can maintain Session and use the long. .. deleting the Session when the user exits the system or expired.2.3.2 stolen session (Session Hijacking)2.3.2.1 attack techniquesThe attack technique that allows the Hacker to impersonate valid users after the victim has to log on to the system by decoding their Session ID stored in a Cookie or URL parameter, hidden variables of the form. Different session fixation attacks, hackers hit the plug in a user's Session ID when they are in your session. And to steal a user's Session ID, hackers can use the following methods: predicted the session (Session ID Prediction)Hackers must be valid users of the system, after several log-in system, Hackers consider valid Session ID received from that search out the rule arises from which can predict the value of a user's session to the next.This technique is very difficult and the probability is not high demand the Hacker must have persistence and brains this little method should work. Suppose your web server use "random" to give France the Session ID, the Hacker cannot detect the session was. Things like "hug trees waiting Hare" is. exhaustion session (Brute Force ID)Hackers used a program to send multiple requests over a period of time to the server. Each request includes a Session ID for Session ID already exists. Hackers rely on habits of application developers such as taking time or the user's IP address to create the Session ID to limit the scan.With the way this is also close to predicting the session should also not be used, to spend so much time but if hackers have insights to that server or application programmer who writes there is very likely going to capture the Session ID. querying to steal the sessionBy inserting a malicious piece of code executed on the victim's browser, hackers can trick the user through a connection in email or put up a phishing site would know that the implementation of the user's Cookie theft and how this is done through Cross-Site Scripting bug (next section will present clearly this technique). After a user's session, hackers into a user's session and exploitation.2.3.2.2 security measures to overcomeThe algorithm creates a Session ID is a big problem and need updated information to change the algorithm for the stronger algorithms.With Session ID too short, hackers can use the technique of "exhaustion". But not so for that extra security with Session ID'S long and complex because of the size of the Session ID is also a big problem.2.4 DENIAL of SERVICE (DOS)2.4.1 The target of DOS attacksA DOS attack is a type of attack make network service paralyzed, no longer meet the requirements anymore. This attack type affects network system, very easy to make and very difficult to protect the system from a DOS attack. Essence of DOS's Attacker would constitute a large amount of network resources such as bandwidth, memory, and losing the ability to process the service request to the other client. The goals of the DOS target as follows: the disksThis is the classic type of attack is filling up the hard disk of the system. The hard disk may be full and can not be used. This type of attack is now almost never used anymore. the RamAttacks on occupying a large space on the RAM can also cause the problem of destroying the system. Buffer overflow attack pattern is a typical. the BandwidthThe bandwidth for each system are restricted, so if Hackers send multiple requests to the system then the bandwidth will not sufficient response to a large volume of data.For example, 11/2011 http://www.vietnamnet.vn website has been Hacker attacks making the network the stagnation could not work and after nearly a month of fighting with DDOS'd works normal again. the Swap SpaceMost of these systems have a few hundred MB of space switch (Swap space) to serve the client requests. Swap space is often used for any child process whose time should DOS can be based on the method to do full swap space to the system does not cater for the guests who would like to use.2.4.2 attack techniques traditional DOS attack SYN FloodBefore learning about traditional DOS attack we need to grasp the principle of operation of the packet with the TCP protocol. TCP is connection oriented protocol, to start the connection, then there will be a 3-step handshake process, while data exchange will have the ACK packets to the packet message success or not and before the disconnect between parties make and receive the 4-step process to end. So now we will learn about the 3-step handshake because this section is relevant to DOS.
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