SYN flooding involves sending numerous SYN packets to the machine to be

Syn flooding involves sending numerous syn packets to

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SYN flooding involves sending numerous SYN packets to the machine to be silenced but never completing the TCP handshake protocol. This attack sends so many SYNs that it fills the OS buffer and prevents any other handshake processing. While the buffer is full, the OS won’t respond to any incoming connection attempts, not even the ACKs that are sent as a by-product of the IP spoofing attack. Attacker probes for a weakness in A’s TCP stack. When one computer sends a SYN packet, it generates an Initial Sequence Number (ISN). It expects that the other end of the connection will ACK with the same ISN (plus 1, remember, b/c the ACK indicates the next byte the ACKer expects to receive). Attacker pretends to be B. The attacker sends a SYN packet from an outside connection that is being spoofed as a trusted source (B). The target machine (A) replies with a SYN/ACK that the attacker never sees – it goes to the real B. However, armed with a predictable sequence number, the attacker completes the three-way handshake by sending an ACK to the target. Make ‘A’ Defenseless. Mitnick’s next move was to use the sequence number data gained from his probes, he was able to make a good guess as to the next ISN the X terminal would try to use. Once connected to the X terminal’s remote shell service. Mitnick mimicked the rsh protocol, lying to the terminal that his connection was coming from the server’s root user. Note: ISN guessing has one slight drawback: It only works against idle machines. Finish the job. Once successfully logged in, Mitnick modified root’s .rhosts file to ensure that any user from any other machine on the Internet could log in as root on the X terminal without being challenged for a password. This was needed to ensure he could log on in the future. The command he issued was echo++>> /.rhosts. This adds ++ to the file, allowing any user from any host to connect to the machine. Method of Attack In the classic sense of a planned attack, executed by a hacker with malicious intent, a sequence of events typically takes place. First, the recon phase , the attacker probes the systems(s) or network(s) to get a sense of what is out there. Next, after discovering potential targets, the attacker performs more thorough system scanning, if necessary, and begins the process of enumeration. With enumeration, the attacker attempts to gain 29
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some actual information about the network or system’s users, specific system names, open shares, SNMP or LDAP directories, and so on. Finally, using any number of methods, the attacker actually attempts to penetrate the system or network and gain access and control of the resource in question. Subverting Access Control Trojan Horses are programs that must be installed or executed by a user to be effective. Often, these are disguised as helpful or entertaining programs which can include OS patches or games.
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  • Spring '14
  • MelvinMasuda
  • Project Management, Transmission Control Protocol, Internet Protocol Suite

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