You should change them if you feel you are at risk. But I am told that there is little risk in writing them down, and that the old advice, never to write them down, is now regarded as history. It appears that experts in crime now say that, people who break into your house or steal your bag, are almost never the same criminals who drain money from your accounts on-line. Nor are they in contact with them.

If you want to be extra safe it is easy to think of a simple code or cypher to use when writing them down, or you can add an extra bit to all of them which you don't write down, but it is easy to remember because it is always the same. Such as. "I always add my initials backwards to the end of all my passwords. "