A "SYN Attack" is a Denial of Service (DoS) attack that consumes
all the resources on your machine, forcing you to reboot.
Denials of Service attacks (attacks which incapacitate a server
due to high traffic volume or ones that tie-up system resources
enough that the server cannot respond to a legitimate connection
request from a remote system) are easily achievable from
internal resources or external connections via extranets and
Internet. Enabling TCP SYN Cookie Protection will help to
eliminate the problem. Edit the sysctl.conf file (vi
/etc/sysctl.conf) and add the following line: # Enable TCP SYN
Cookie Protection net.ipv4.tcp_syncookies = 1 Once the
configuration has been set, you must restart your network for
the change to take effect. The command to restart the network is
the following: To restart all network devices manually on your
system, use the following command: [root:~ ]#
/etc/rc.d/init.d/network restart