In case yesterday's backup horror story didn't scare youenough, here's an incomplete list of things that have been known to gowrong with backups. Are you sure that none of them are happening toyour backups right now?

• the backup program writes corrupted backups.
• the backup program doesn't capture a usable system state becausethings keep changing even as it runs (databases are famous forthis).
• the backup program generates incomplete backups, especially when runin incremental mode. For example, many

Backups have been in the geek news recently, courtesy of thechilling tale of the online comic Penny Arcade's backup failure .Making backups is important, but there's an equally important and farless appreciated piece: checking your backups to make sure that youcan actually restore them .

You may say 'but, I'm sure my system would scream a lot if somethingwas wrong'. Let me tell you a story about that.

Once upon a time there was a young and innocent systemadministrator.

One form of blog spam is 'Referer' spam. Referer is the (optional)HTTP header included in requests from web browsers to web servers thatcontains the web page that the link to your page was on. Some blogsoftware uses this header as a lower-tech version of Trackback .

Referer spam has the attraction for the spammers that it's dirt simpleto do. All their software has to do is to make an ordinary HTTPrequest for a page or three on a web site and throw in a

Overall SMTP connections are running at twice the expected rate, at246,000 SMTP connections although only from the usual 33,000 differentIP address. The SMTP frontend hit a highwater of 18 simultaneousconnections during the week.

Kernel level IP filtering:

Host/Mask           Packets   Bytes204.50.22.50          11909    572K170.206.225.64         8186

Yesterday's entry mentioned in passingfixing a bug in DWiki . Today's entry is about the anatomy of that bug(and how I found it).

This starts with DWiki 's processing model, which involves displayingpages in a number of different formats, which are called'views'. (More about this is in ProcessingModel .) Not allviews are valid for all pages (for example, the ' history 'view isn't valid for a file without a version history).

If an