Knight Ridder/Tribune News Service

Microsoft blocks and erases MSN Internet blogs that the Chinese government doesn't like. Following Chinese rules, Microsoft won't allow "forbidden language" such as "Tibet Independence" or "Tiananmen massacre."

Yahoo gave the identity of a dissident to the Chinese government which then jailed him for 10 years for e-mailing "state secrets" (details of a crackdown on dissent) to an American Web site. Shi Tao used Yahoo Mail to send the message, which meant Yahoo could find his "IP" address in their records and give it to the government.

Why did Microsoft and Yahoo obey these Chinese demands? Probably because they want to continue to do business in China, valuing revenue over rights. And I think that's just wrong.

Back in the USA, you may have heard that Microsoft, AOL, and Yahoo recently gave their Internet search records to the U.S. government. Supposedly these records were anonymous, simply a list of how often different words were searched for, without personal information such as individual IP addresses that tell who searched for what. Google so far has refused to hand over its search records (thank you Google).

The U.S. government apparently wants to use search requests as evidence to resurrect the COPA (Child Online Protection Act) that the Supreme Court blocked as unconstitutional. This isn't, by the way, about "child pornography," as some news reports say, but about children viewing pornography.

How could search records be traced back to individuals, to you? Through IP addresses, the same way Shi Tao was caught in China. Each time you search, each time you visit a Web site, that site can see and record your IP.

Protecting children may sound admirable, but you probably wouldn't want a government or anyone else to have unrestricted access to your IP search history. Who knows what the results would be? For example, an insurance company might refuse to insure anyone who frequently looked up "Alzheimer's." Or a government bureaucrat might put you on the "No Fly" list if you or someone using your computer looked up "Bin Laden" or "Al Jazeera" too often.

So what is an IP?

Each computer connected to the Internet gets its own IP (Internet Protocol) address, the same way each house gets its own "snail mail" street address. That's how the bits of information are able to travel from one computer to just the right other computer online - each little packet of bits is labeled with the destination IP.

My computer's IP was 4.178.108.170 while I researched and wrote the first half of this column. IPs are always a series of four numbers like that, separated by periods. (Soon we may all be upgraded to a series of six numbers -- called IPv6 -- because there are so many computers coming online.) I looked my IP up by going to http://internetfrog.com with my web browser, and double-checked at other sites such as http://megawx.aws.com/support/faq/software/ip.asp, http://www.ipaddressworld.com, and http://privacy.net.

After I disconnected and took a break, then dialed in again, my IP was 4.178.135.144. Dialup connections use "dynamic" IPs, assigning a new one each time you get online. But your Internet Service Provider will keep records of which IP you had for each session, and would be able to tell authorities who you were from that IP.

Many high-speed broadband connections, such as DSL and Cable, use or at least offer the option of "static" IPs: your computer gets one IP number and keeps it. That lets you run a Web site on your computer, one that other people can connect to. Any big Web site you visit also has a permanent IP. No matter the domain name you type into your browser -- such as Amazon.com or MyFriendsBoringBlog.com -- a program on the Internet automatically translates that into the assigned IP. A downside of a static IP is that they're easier for hackers to attack, because you're always in the same place online.