Many gurus will stress the importance of making backups of your blog or website in case your website is hacked or a “routine” software update goes wrong. This is excellent advice; particularly if you store the backups offline rather than in your webspace.
There is quite a range of software available which will do this automatically. Backup files can however be very large so many of these programs will create rolling backups which consist of, typically, the backups from each day of the last week. When they have created the backup on day 8 they delete the day 1 backup and then when they create the day 9 backup they delete the day 2 backup. This keeps the repository containing the stored backups at a managable size and ensures you have a weeks worth of the freshest daily backups.
The idea of an automatic 7 day rolling backup sounds very efficient.
The problem with this approach is that many different things can go wrong with your website and not all of them are immediately obvious. There are, for example, many different types of hacker. The ones which get most publicity are perhaps the “script kiddies” which take delight in defacing a website, or maybe even delete it entirely, and replace it with their name or slogan. If your blog is hacked like this then it is obvious and will be seen quite quickly. You then have the organized gangs who are more subtle and just insert links on your pages to their various pharmacutical websites. These are more difficult to spot but may be seen by your regular visitors who may let you know. However there also a much more stealth hacker who takes great care not to leave any visible sign that they have gained access and instead concentrates on changing all the links of all your ads, and affiliate links, to their own. You blog/website looks untouched and behaves perfectly normally and may go undetected for weeks, maybe even a month or more, before your suspicions are aroused and you realize something is wrong. By that time all your rolling backups contain the corrupted code.
Do not therefore just rely on rolling 7 day backups. Make sure that as well as these you permanently archive one backup a week. That way you should be able to find a “clean” backup you can use (even if it is a few weeks old) should you become the victim of a stealth hacker.