Phoning home facts for kids

In computing, phoning home is a term used when a computer or a software program sends information back to another computer, often its creator or owner. This information can include things like where the computer is located, the username, or other details.

Sometimes, phoning home is very helpful. For example, if a laptop gets lost or stolen, this feature can help track it down. Many companies use this on their work laptops. It usually involves a special program that's hard to find or remove. However, phoning home can also be used for bad reasons, like when apps or hardware secretly send your data to their makers without you knowing. This information might even be hidden (encrypted) so you can't easily see what's being sent.

For example, the famous Stuxnet cyberattack on Iran's nuclear facilities used phoning home technology.

Why do computers "phone home"?

Computers and software "phone home" for many different reasons, some good and some not so good. Let's look at some common uses.

Legal uses of phoning home

Some ways that computers "phone home" are perfectly legal and helpful.

• Checking software licenses: Imagine you buy a software program like Adobe Creative Suite. When you open it, the program might "phone home" to check its serial number. If the number is already being used by too many people, or if it's fake, the program might ask you to enter a correct one. If you don't, it might only work in a trial mode. You can sometimes stop this by turning off your internet or using a firewall to block the connection.
• Marketing and understanding users: Some companies use phoning home to learn about how people use their products. For instance, a digital video recorder (DVR) might report what TV shows you watch. Older music CDs, like those from the "Sony BMG Rootkit" issue, even sent information about what music was being played.
• Maintenance and repairs: Big computer systems, like mainframes (very powerful computers used by large organizations), have used phoning home for many years. They can alert the manufacturer if there's a problem with their hardware. This helps get repairs done quickly, sometimes even before the user notices a problem! Large copy machines also use this to track how many copies are made (for billing) and to report if they need maintenance.
• Tracking software use for research: In research, phoning home helps track how often open-source software (software that anyone can use and change) is used. This information helps researchers get funding to keep improving the software.
• Finding lost or stolen devices: One very useful way phoning home is used is to track lost or stolen computers, especially laptops. Software like Absolute Software's CompuTrace regularly sends information to a special server. This information can then be used by companies or the police to find a missing computer.

How documents and emails can "phone home"

It's not just applications that can "phone home"; sometimes, even documents or emails can do it!

• Tracking document views: Some documents, like PDF files, can be set up by their creators to "phone home." This means the document tries to connect to the author's website, which can help the author track how many times the document is viewed. For example, older versions of Adobe Reader started showing a warning when a PDF tried to do this.
• Email tracking (web bugs): HTML e-mail messages can also "phone home." When you open an email, it might need to download images or other files from a web server. When your computer asks for these files, it sends its IP address (like a computer's street address) to the server. The server can then use this information, along with other details hidden in the file's address (URL), to figure out who you are, what marketing campaign you're part of, and more. These hidden tracking elements are sometimes called "web bugs." To protect your privacy, many e-mail clients (like Outlook or Gmail) don't automatically load images in emails. They give you the option to load them only if you trust the sender.

Malicious uses of phoning home

Unfortunately, "phoning home" can also be used for harmful purposes by malware (malicious software).

• Spying and data theft: Many types of malware can "phone home" to collect and store information about your computer and what you do on it. For example, a type of malware called the Pushdo Trojan was known for its ability to send many different harmful programs to infected Windows computers. This shows how complex modern malware can be and how it uses phoning home to spread and gather information.

See also

In Spanish: Llamada a casa para niños