The simple idea behind PayPal -- using encryption software to allow people to make financial transfers between computers -- has turned into one of the world's primary methods of online payment. Despite its occasionally troubled history, including fraud, lawsuits and zealous government regulators, PayPal now boasts more than 100 million accounts worldwide [ref].

In this article, we'll show you how to use PayPal, find out how the transactions are made, and learn something about the company's history. We'll also examine some of the complaints about PayPal's business practices.

PayPal is an online payment service that allows individuals and businesses to transfer funds electronically. You can use it to pay for online auctions, purchase goods and services, or to make donations. You can even use it to send cash to someone.

A basic PayPal account is free. You can send funds to anyone with an e-mail address, whether or not they have a PayPal account. They'll get a message from PayPal about the funds, and then they just have to sign up for their own account.

Funds transferred via PayPal reside in a PayPal account until the holder of the funds retrieves them or spends them. If the user has entered and verified their bank account information, then the funds can be transferred directly into their account. Other ways to withdraw your funds are listed below.

Signing up for PayPal is quick and doesn't even require you to enter any bank account information, although a checking account or credit card is required to use many of PayPal's features. From the PayPal homepage, just click on the "Sign Up Now" button. At the next page, you'll choose whether you want a personal, business or premier account. If you just plan to use PayPal for the occasional eBay auction or online purchase, a personal account is the right choice. If you intend to use PayPal to accept payments for your own business, then a business or premier account would be more suitable. If you select a personal account, you can upgrade in the future.

From there, you will go to a page that asks for your basic personal information -- your name, address, telephone number and e-mail address. You will also be required to enter two security questions in case you lose your password, and you have to enter a randomly generated series of letters and numbers, which help prevent fraud. Once you confirm your account by following instructions you'll receive via e-mail, the sign-up process is done.

Adding a valid, current credit card to your account will allow PayPal to confirm your address (if it matches where you receive your credit card statements). Having a confirmed address shows both buyers and sellers that you are less likely to be a scammer. You can also use your credit card for PayPal's Expanded Use service, which allows you to draw money from the credit card, instead of just from a bank account.

If you want to add funds to your PayPal account from your checking account, or vice versa, you need to enter and verify your bank account with PayPal. When you enter your account number and routing number, PayPal will make two micropayments to that account. These payments are usually about 5 cents. PayPal will then ask you to enter those amounts in order to verify the account (they'll show up on your bank statement). After you enter them, your bank account will be ready for use.

Just about every peripheral made now comes in a USB version. Here's a list of some of the USB devices that you can buy today:

• Printers 
• Scanners 
• Mice 
• Joysticks 
• Flight yokes
• Digital cameras 
• Webcams 
• Scientific data acquisition devices
• Modems 
• Speakers 
• Telephones 
• Video phones
• Storage devices like Zip drives
• Network connections 

OK

The easy solution to the problem is to buy an inexpensive USB hub. The USB standard supports up to 127 devices, and USB hubs are a part of the standard.

A hub typically has four new ports, but may have many more. You plug the hub into your computer, and then plug your devices (or other hubs) into the hub. By chaining hubs together, you can build up dozens of available USB ports on a single computer.

Hubs can be powered or unpowered. As you learn in How USB Ports Work, the USB standard allows for devices to draw their power from their USB connection (all USB cables contain two wires -- for +5 volts and ground). A high-power device like a printer or scanner will have its own power supply, but low-power devices like mice and digital cameras get their power from the bus. The power (up to 500 milliamps at 5 volts) comes from the computer. If you have lots of self-powered devices (like printers and scanners), then your hub does not need to be powered -- none of the devices connecting to the hub need additional power, so the computer can handle it. If you have lots of unpowered devices like mice and cameras, you probably need a powered hub. The hub has its own transformer, and it supplies power to the devices that connect to the hub so the devices do not overload the computer's power supply.

The Universal Serial Bus can easily handle both a scanner and a printer, even if you are scanning and printing at the same time. The original USB supports up to 12 megabits per second, and USB 2.0 supports up to 480 megabits per second -- considering that most devices consume only 6 megabits per second, you can definitely run more than one device at a time.

For example, experts estimate that the Mydoom worm infected approximately a quarter-million computers in a single day in January 2004. (Times Online). Back in March 1999, the Melissa virus was so powerful that it forced Microsoft and a number of other very large companies to completely turn off their e-mail systems until the virus could be contained. The ILOVEYOU virus in 2000 had a similarly devastating effect. That's pretty impressive when you consider that the Melissa and ILOVEYOU viruses are incredibly simple.

In this article, we will discuss viruses -- both "traditional" viruses and the newer e-mail viruses -- so that you can learn how they work and also understand how to protect yourself. Viruses in general are on the wane, but occasionally a person finds a new way to create one, and that's when they make the news.

When you listen to the news, you hear about many different forms of electronic infection. The most common are:

• Viruses - A virus is a small piece of software that piggybacks on real programs. For example, a virus might attach itself to a program such as a spreadsheet program. Each time the spreadsheet program runs, the virus runs, too, and it has the chance to reproduce (by attaching to other programs) or wreak havoc.

• E-mail viruses - An e-mail virus moves around in e-mail messages, and usually replicates itself by automatically mailing itself to dozens of people in the victim's e-mail address book.

• Worms - A worm is a small piece of software that uses computer networks and security holes to replicate itself. A copy of the worm scans the network for another machine that has a specific security hole. It copies itself to the new machine using the security hole, and then starts replicating from there, as well.

• Trojan horses - A Trojan horse is simply a computer program. The program claims to do one thing (it may claim to be a game) but instead does damage when you run it (it may erase your hard disk). Trojan horses have no way to replicate automatically.

Computer viruses are called viruses because they share some of the traits of biological viruses. A computer virus passes from computer to computer like a biological virus passes from person to person.

There are similarities at a deeper level, as well. A biological virus is not a living thing. A virus is a fragment of DNA inside a protective jacket. Unlike a cell, a virus has no way to do anything or to reproduce by itself -- it is not alive. Instead, a biological virus must inject its DNA into a cell. The viral DNA then uses the cell's existing machinery to reproduce itself. In some cases, the cell fills with new viral particles until it bursts, releasing the virus. In other cases, the new virus particles bud off the cell one at a time, and the cell remains alive.

A computer virus shares some of these traits. A computer virus must piggyback on top of some other program or document in order to get executed. Once it is running, it is then able to infect other programs or documents. Obviously, the analogy between computer and biological viruses stretches things a bit, but there are enough similarities that the name sticks.

What's a "Worm"?
A worm is a computer program that has the ability to copy itself from machine to machine. Worms normally move around and infect other machines through computer networks. Using a network, a worm can expand from a single copy incredibly quickly. For example, the Code Red worm replicated itself over 250,000 times in approximately nine hours on July 19, 2001.

A worm usually exploits some sort of security hole in a piece of software or the operating system. For example, the Slammer worm (which caused mayhem in January 2003) exploited a hole in Microsoft's SQL server. This article offers a fascinating look inside Slammer's tiny (376 byte) program.

Worms use up computer time and network bandwidth when they are replicating, and they often have some sort of evil intent. A worm called Code Red made huge headlines in 2001. Experts predicted that this worm could clog the Internet so effectively that things would completely grind to a halt.

The Code Red worm slowed down Internet traffic when it began to replicate itself, but not nearly as badly as predicted. Each copy of the worm scanned the Internet for Windows NT or Windows 2000 servers that do not have the Microsoft security patch installed. Each time it found an unsecured server, the worm copied itself to that server. The new copy then scanned for other servers to infect. Depending on the number of unsecured servers, a worm could conceivably create hundreds of thousands of copies.

The Code Red worm was designed to do three things:

• Replicate itself for the first 20 days of each month
• Replace Web pages on infected servers with a page that declares "Hacked by Chinese"
• Launch a concerted attack on the White House Web server in an attempt to overwhelm it

The most common version of Code Red is a variation, typically referred to as a mutated strain, of the original Ida Code Red that replicated itself on July 19, 2001. According to the National Infrastructure Protection Center:

The Ida Code Red Worm, which was first reported by eEye Digital Security, is taking advantage of known vulnerabilities in the Microsoft IIS Internet Server Application Program Interface (ISAPI) service. Un-patched systems are susceptible to a "buffer overflow" in the Idq.dll, which permits the attacker to run embedded code on the affected system. This memory resident worm, once active on a system, first attempts to spread itself by creating a sequence of random IP addresses to infect unprotected web servers. Each worm thread will then inspect the infected computer's time clock. The NIPC has determined that the trigger time for the DOS execution of the Ida Code Red Worm is at 0:00 hours, GMT on July 20, 2001. This is 8:00 PM, EST.

Upon successful infection, the worm would wait for the appointed hour and connect to the www.whitehouse.gov domain. This attack would consist of the infected systems simultaneously sending 100 connections to port 80 of www.whitehouse.gov (198.137.240.91).

The U.S. government changed the IP address of www.whitehouse.gov to circumvent that particular threat from the worm and issued a general warning about the worm, advising users of Windows NT or Windows 2000 Web servers to make sure they have installed the security patch.