For this example we'll have two servers, one named Johnny and another named Cash. Both are running openssh. Our goal is to have a program on Johnny login to Cash and run a program on Cash. To make task a little more complex we'll be using different users on each machine.

The first thing we'll need to do is generate public and private keys on Johnny. So, logged into Johnny as user 'boy' we create public and private keys by creating them in .ssh directory as follows:

Johnny$> pwd /home/boy/.ssh Johnny$> ssh-keygen -t rsa -f sue Generating public/private rsa key pair. Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in sue. Your public key has been saved in sue.pub. The key fingerprint is: 8d:e9:c0:g1:c7:1f:e3:b3:2f:38:12:aa:b5:3b:2e:b3 boy@Johnny Johnny$>

In example above we picked an arbitrary name, sue, to identify files that hold generated keys. When prompted to enter a passphrase (twice) we simply hit enter twice.

As output of ssh-keygen indicates, public key has been saved in a file named sue.pub.

The output of ssh-keygen implies, but doesn't indicate directly, that private key is in a file named sue (Yes, a user named boy created a file named sue.)

Johnny$>ls -l -rwx------ 1 sue suegrp 887 Oct 17 14:27 sue -rwx------ 1 sue suegrp 223 Oct 17 14:27 sue.pub

The private key file, sue, will remain on Johnny for reaminder of this exercise, but public key must be moved to remote server, Cash. Note that .ssh directory itself, as well as sue and sue.pub files should have permissions of 700.

Now you'll need to ftp sue.pub file from Johnny to Cash. The user on Cash that we'll login as is user 'named'.

Malicious codes come in three basic formulas.Viruses are small programs that reproduce themselves for purpose of causing some damage.

Trojan Horses are disguised as gifts which may come as an attachment in your email.Once ran its purpose is to cause do harm to your system as well.

Then you may come in contact with does worms which cause damage by copying themselves over networks as wells as individual systems.These codes alters not just one system but several within a network.

After you enhance your knowledge of malicious code, know symptoms of an infected system.Strange PC behavior,an increase or decrease of data in a file, pop up messages,random graphics,and files being deleted are some symptoms of your system having a virus.

The best way to find and remove viruses is with installation popular anti virus software from Norton or McAfee.These programs readily identify infections as well as promptly remove them.