Yuki, Moodle can be attacked like any other software and it relies just as heavily on your system security as does any other software. But I would suggest that there are many there products from major software companies that represent a bigger risk than Moodle. Moodle security is actually pretty good, even within Moodle but I suggest it could be even less likely that your system can be compromised by Moodle than it can by any other software.
Any Moodle Administrator can wreck a Moodle, from inside - just as any Network Administrator can wreck a network from inside so the risk is the same - but the damage of a broken Moodle that has been properly backed up and maintained is very easily repaired. 22 minutes to a working Moodle, including deleting the damaged Moodle and download
time for a later version, and then about 3 - 4 hours to restore about 200 odd courses and all users. This was all done manually, slowly. I am sure that an automated restore would have been a lot quicker, but that does not help my sense of self importance.
. Most users did not even realize the Moodle was down.
Proper mirroring would get around even that issue.
Security from within Moodle is actually pretty good, but any skilled hacker can break any system, from within.
All the core modules and activities
are well tested and reliable, and if you look at what people write in these forums, by far the largest number of problems come from people who have done something to their Moodle and broke it. Genuine bugs are few and far between and for a product that works over all the major platforms, and most of the minor ones, that is something few other products can boast. Many of the other type are questions about just doing things, or perhaps attempts at expanding what Moodle actually does, or doing it differently.
The learning curve of Moodle is better than many other proprietal programs, and while it may not always be intuitive, it is very clear in what it does and where. I am mostly self taught, like most people here. I was using Moodle for months, relying on MoodleDocs
for information, not even realizing that Moodle Forums were available to me, before I stumbled into them. I am embarrassed to admit that it was permissions and Roles that got me.. where I needed most help and got it.
It is that more than anything that should sway any decision. You get a problem you can usually get an answer or a fix within hours. Can't say that about many other programs. That rapid turn around saves a lot of money in downtime. And if there is a huge problem, the latest version of Moodle can be downloaded and installed within 22 minutes. Courses can be replaced within hours and most users will not even realize there was a problem.