Often customers run offline systems and claim that such machines do not need updates since they are offline. But this is a fallacy: updates do not only close security holes but also deliver bug fixes – and they can be crucial.
Background
Recently a customer approached me with questions regarding an upgrade of a server. During the discussion, the customer mentioned that the system never got upgrades:
“It is an offline system, there is no need.”
That’s a common misconception. And a dangerous one.
Many people think that updates are only important to fix security issues, and that bugfixes are not really worth considering – after all, the machine works, right?
Wrong!
Software is never perfect. Errors happen. And while security issues might be uncomfortable, bugs in the program code can be a much more serious issue than “mere” security problems.
Example One: Xerox
To pick an example, almost each company out there has one type of system which hardly ever gets updated: copy machines. These days they are connected to the internet and can e-mail scanned documents. They are usually never updated, after all it just works, right?
In 2013 it was discovered that many Xerox WorkCentres had a serious software bug, causing them to alter scanned numbers. It took quite some weeks and analysis until finally a software update fixed the issue. During that time it turned out that the bug was at least 8 years old. So millions and millions of faulty scans have been produced over the years. In some cases the originals were destroyed in the meantime. It can hardly be estimated what impact that will have, but for sure it’s huge and will accompany us for a long time. And it was estimated that even today many scanners are still not patched – because it is not common to patch such systems. Offline, right?
So yes, a security issue might expose your data to the world. But it’s worse when the data is wrong to begin with.
Example two: Jails
Another example hit the news just recently: the US Washington State Department of Correction released inmates too early – due to a software bug. Again the software bug was present for years and years, releasing inmates too early all the time.
Example three: Valve
While Valve’s systems are often per definition online, the Valve Steam for Linux bug showed that all kinds of software can contain, well, all kinds of bugs: if you moved the folder of your Steam client, it could actually delete your entire (home) directory. Just like that. And again: this bug did not happen all the time, but only in certain situations and after quite some time.
# deletes your files when the variable is not set anymore rm -rf "$STEAMROOT/"*
Example four: Office software
Imagine you have a bug in your calculating software – so that numbers are not processed or displayed correctly. The possible implications are endless. Two famous bugs which shows that bugfixes are worth considering are the MS Office multiplication bug from 2007 and the MS Office sum bug from a year later.
Example five: health
Yet another example surfaced in 2000 when a treatment planning system at a radiotherapy department was found to calculate wrong treatment times for patients and thus the patients were exposed to much more radiation than was good for them. It took quite some time until the bug was discovered – too lat for some patients whose
Conclusion
So, yes, security issues are harmful. They must be taken serious, and a solid and well designed security concept should be applied. Multiple layers, different zones, role based access, update often, etc.
But systems which are secured by air gaps need to be updated as well. The above mentioned examples do not show bugs in highly specific applications, but also in software components used in thousands and millions of machines. So administrators should at least spend few seconds reading into each update and check if its relevant. Otherwise you might ignore that you corrupt your data over years and years without realizing it – until its too late.
CentOS 7 is out. With systemd, Docker integration and many more fixes and new features I wanted to see if the new remote upgrade possibility already works. I’ve already posted the procedure to 
/home/liquidat 