Almost every major site on the Net now uses them - even sites with nothing to sell, just out of sheer nosiness. So, go check your hard drive and see how many cookies you have collected - you may be in for a shock. Most electronic mail on the Internet is about as private as a postcard. After it leaves the sender's computer, the message jumps from one network server to the next as it streams toward the recipient. The problem is, it's easy for a hacker to intercept the message en route and impossible to tell if anyone else has read this supposedly private correspondence before it reaches its destination.
Hackers use various tricks to hijack e-mail as it passes between servers.
Hackers could run a program that cycles through every permutation of simple passwords until it hits on one that unlocks the network. Or they could attach themselves to a company's World Wide Web server,which is often left outside the firewall, since it's considered an external site,and then slip into the company's network as if they were internal users. E-mail is irresistible to eavesdroppers, because it's often full of juicy information, from secret corporate strategies to credit card numbers. Some e-mail contains headers with logins and passwords, allowing hackers to sign on and gain complete access, even to secure areas. The only way to safeguard e-mail from eavesdroppers is by encrypting it,scrambling the message so it can be read only by the intended recipient.