Using a Computer Safely
Staying safe with other people online
Work out how far something you post really travels once other people pass it on, and follow a fixed set of steps when a message is meant to hurt.
Most of what this course has been about is machines, and machines are predictable. Other people are not, and there are exactly two things another person can do with something you post that no machine does on its own. The first is pass it on to people you never chose, and that one is arithmetic — you can work out how far a post travels as surely as you can work out what a loop prints. The second is be somebody other than who they say they are, and that one is not arithmetic at all, which is why the rest of this lesson is a fixed set of steps rather than a sum.
Reach multiplies, and deleting does not reach copies
If you send something to a group and every person in that group sends it to some number of others, the second round is the size of the group multiplied by that number — not added to it. Rounds add up, but each round is worked out by multiplying. And the copies other people have made are not yours to delete: deleting your own copy removes exactly one of them, however early you do it.
When a message is meant to hurt
Four steps, and the order of the middle two is not an accident. Do not reply — a reply is the thing the message was sent to get, and giving it back is what keeps the sender going. Keep it: take a picture of it while it is still on the screen. Block the sender, which is done after keeping the copy because blocking can take the message away with it. Then tell an adult you trust. Passing the message round your friends is not one of the four steps, and neither is deleting it, however much you want it gone.
Worked example
You post something to 30 people. Six of those 30 pass it on to 20 people each, and nobody else passes it on. How many people besides you have seen it?
Thirty people have it from you directly.
This is the round that is easy to forget later, because it happens before any passing on and feels like it does not count.
Try it together
A message goes to a group of 12 people. Every one of the 12 passes it to 5 more, and every one of those passes it to 2 more.
Three rounds. Take them one at a time and add nothing until the end.
1.How many people are reached in the second round?
Have a go
Have a go on your own. A message is sent to 8 people and each of them sends it to 7 more. How many people besides the sender have seen it?
Ready to practise?
Eight questions on what you have just read. Nothing is timed, and you can play as many times as you like.