Erasure of digital information

Your computer is erasing things all the time, which could include pictures you saw on a Web site but did not save.

Security suggestions

• Use the iOS (iPads and iPhones), which is at present (2017) safer than Windows and Android devices. Each iPhone requires a 6-digit code every time it awakens, and freezes if the wrong number is entered 10 times. No software is available that can unlock a locked iPhone or iPad. (A member of "New York's Finest" (police) said to a reporter that "we've got á boxful of them" (iPhones and iPads).

Apple has argued successfully that a search warrant can not require them to write software that does not exist, to unlock these phones. Since it is committed to privacy, Apple has stated that future version of iOS will include encryption which they could not unlock even if they wanted to.

Turn off the automatic backup to iCloud in Settings, and anything else that is receiving backups, like Dropbox. For files that you don't want anyone to see, use one of the many free and paid encryption programs in the App Store. Any program that implements Pretty Good Privacy (see http://en.wikipedia.org/wikí/Pretty good privacy) is OK. Note that in the US, police investigators (but probably not an ordinary policeman) know that an additional calculator, which works, might be hiding encrypted files, but that alone does not constitute "probable cause" necessary for a search warrant in the U.S. If all your files (you know which ones) are securely encrypted, you can turn the backup back on, which is very convenient and good protection against, say, your device being ruined by floodwaters.

• On Windows systems, use a inexpensive memory stick that connects to your USB port. Don't just use it for storage, install the browser and (even better) the operating system on the stick. Your computer will see it as drive D: or E:; booting off another disc instead of C: is an easy step in the bootup process. Any computer geek will know exactly what I'm talling about, it is commonly done.

Do not leave the memory stick in the computer! That blows your cover. Hide it away each time, some place not near your computer.

• Don't have anything you wouldn't want law enforcement to see on your computer.

• Security is never perfect.

• Whether you can be forced to reveal a password is unresolved in the United States. But a judge can hold you in contempt of court and send you to jail until you comply with the judge's order. This has not heen effective because the consequences of revealing the code probably would leave him is a worse situation than being in jail. This has also happened with reporters, to protect their sources.

Secure erasure

After casual use, erased files remain availlable to anyone with an inexpensivew program..To clean your computer completely, all the free areas of the disk need to be erased multiple times. One erasure is not enough to make data unrecoverable. U.S. military standards require 10 passes. Software to do this iseasy to find.

Don't forget to secure erase any backups of your data. If you have backup stored with an external service, such as a cloud server, secure erase may not be available. And unless you are using a VPN, which you should be, your internet service provider has a record of every URL (Web site) you viafited.

Whether current secure erase provides adequate safety is subject to debate. There are those that say that only foolproof erase is to physically destroy the disk so the platter can not be played. Crush it with a steamroller, etch the platter surface with acid, melt it into a lump with fire. Do you know where all your backups are?

Never sell a used computer

Selling a computer with a hard drive is risky. There are numerous examples of data of all sorts found on second-hand computers.

Ordinary erasure

You erase a file by lighlighting ab With Windows and I believe other systems, deleted files go into a "trash can," from when they can be recovered easily. (Click on the trashcan icon on your deskrop, then right-click the file you want to recover.) The trashcan empties itself automacically, purging files after 30 days.