There’s a conflict here in that ECC requires additional storage, effectively reducing that available to the user, and increases its cost per GB. Storage manufacturers now try to reduce the chances of files from becoming corrupted or damaged, for instance using error-correcting codes (ECC) in their products. Overall, files kept on recent storage systems in modern computers are still prone to damage and corruption, although they should be less of a problem than they have been in the past. Such Wholesale encryption of files is quite a different issue, but several malicious apps and PUPs have also corrupted user files, and may do so unintentionally. The best-known examples of malicious software modifying user files are, of course, in ransomware. APFS was designed using the ‘copy on write’ principle which should make this a problem of the past, although in practice it can still occur very rarely. Apple introduced journalling to tackle this, and that has been effective in reducing its occurrence but doesn’t eliminate it altogether. File systems such as HFS+ are particularly prone to this because of the way that they write changes out to disk. One previously common cause of data corruption is failure to complete outstanding disk operations before a forced restart due to a kernel panic or other severe fault. If you’ve ever tried accessing old DVD-R or CD-R storage, you’ll have come across examples where files can only be read with errors, or the whole disk is unreadable, even when it has been stored in good conditions in the dark. All storage media become unreliable with use and time, although meaningful estimates of error rate are very hard to come by. Worst cases result in complete failure of the storage, and send you to your backups, but minor errors and ‘bit rot’ appear more common. Hard disks are well-known for developing errors and ‘bad blocks’ which can corrupt files, and regardless of some claims this remains true to a lesser extent in SSDs. But it can still happen, even with protections such as sandboxes. Thankfully that’s now unusual, and accidental modification of files by other apps should be a rarity. At that time, many apps used to write data using low-level commands for speed. There was a time when it wasn’t uncommon for wobbly apps, often just as they were about to crash, wreaking destruction among files stored on disk. I’m concerned here with the latter three and their variations. malicious software can change the data.the data stored can become altered as a result of failure or ‘bit rot’.non-malicious software can change it accidentally, for example by writing to the wrong file or storage block.we (or a process acting on our behalf) can change it deliberately, by editing the file.There are many different reasons that the contents of a file can become changed, including: It’s one of those things we know from bitter experience isn’t completely reliable, but what more can you do than trust your Mac? This article starts by looking at what can go wrong, and what’s there to prevent it. Over coming articles, I’m going to consider a subject which most of us just take for granted, that the contents of our files can be relied upon – file integrity.
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