HP OfficeConnect Firewall Series Manuel d'utilisateur télécharger pdf (Page 81)

OfficeConnect VPN Firewall User’s Manual Chapter 14. Configuring IPSec VPN

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Description

Windows OS are vulnerable to this attack. If the computers in

the LAN are not updated with recent versions/patches, you are

advised to enable this protection by checking this check box.

TCP/UDP/ICM

P Port Scan

Check or un-check this option to enable or disable protection

against such attacks. A UDP flood is a form of denial of service

attack that can be initiated when one machine sends a large

number of UDP packets to random ports on a remote host. As

a result, the distant host will (1) check for the application

listening at that port, (2) see that no application is listening at

that port and (3) reply with an ICMP Destination Unreachable

packet.

When the victimized system is flooded, it is forced to send

many ICMP packets, eventually making it unreachable by

other clients. The attacker may also spoof the IP address of

the UDP packets, ensuring that the excessive ICMP return

packets do not reach him, thus making the attacker’s

etwork location anonymous.

IP Spoofing

Check or un-check this option to enable or disable protection

against such attacks. IP spoofing is one of the most common

forms of on-line camouflage. In IP spoofing, an attacker gains

unauthorized access to a computer or a network by making it

appear that a malicious message has come from a trusted

machine by ―spoofing‖ the IP address of that machine.

Ping of Death

Check or un-check this option to enable or disable protection

against such attacks. A ping of death is a type of attack on a

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Description

computer that involves sending a malformed or otherwise

malicious ping to a computer. A ping is normally 64 bytes in

size (or 84 bytes when IP header is considered); many

computer systems cannot handle a ping larger than the

maximum IP packet size, which is 65,535 bytes. Sending a

ping of this size can crash the target computer.

LAND Attack

Check or un-check this option to enable or disable protection

against such attacks. A LAND attack is a DoS (Denial of

Service) attack that consists of sending a special poison

spoofed packet to a computer, causing it to lock up.

Echo Chargen

TearDrop

Check or un-check this option to enable or disable protection

against such attacks. A Teardrop attack involves sending

mangled IP fragments with overlapping, over-sized, payloads

to the target machine. A bug in the TCP/IP fragmentation re-

assembly code of various operating systems caused the

fragments to be improperly handled, crashing them as a result

of this.[4] Windows 3.1x, Windows 95 and Windows NT

operating systems, as well as versions of Linux prior to

versions 2.0.32 and 2.1.63 are vulnerable to this attack.

TCP

XMAS/NULL/S

YNFIN Scan

Check or un-check this option to enable or disable protection

against such attacks. During a normal TCP connection, the

source initiates the connection by sending a SYN packet to a

port on the destination system. If a service is listening on that

port, the service responds with a SYN/ACK packet. The client

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HP OfficeConnect Firewall Series Manuel d'utilisateur Page 81

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