A lot is really going to depend on the character. Computers is a huge field and no one is going to know everything. So concentrate mostly on what they seem to know well.
Since you mentioned programming and digital security, those are two good starts. For digital security, I'd recommend this site to start: https://www.allclearid.com/personal/resource-center/
That's a online identity protection service and they have a good blog with resources and basic info on security that is written in a way that even the average user can understand. That's going to get into not only the how to protect yourself sort of deal (which is always useful) but also into the whys and hows on how this stuff happens. Anyone into security is going to know something of how thieves think because that is key to protection. A big idea with security is to make it so you aren't an easy target. This is more on the personal side though, if you are going to need to look into security on a corporate side that's a more tricky beast, but as long as you know basic terms you should be okay for RP. Definitely good stuff to learn even if RP isn't involved since security is important.
As far as programming goes, keep in mind that HTML is programming, so you already have some basics. If your character uses specific programming languages, try and learn something about those. If there isn't anything specific, I'd advise to try and learn a bit about CSS. CSS is a nice addition to knowledge of HTML and can be useful to you and learning some basics on it will give you some more in depth knowledge on programming and how programmers have to think. Try just learning some basics on it and see if you can play around with tweaking some code for your journal or plurk layouts. That will give you a better idea of what your character does and it's good practical knowledge as well. Even stuff like changing around your color scheme teaches a bit about how the code works.
Good luck to you! It's a complex and vast topic, but at least there are some things that are good to learn that you'll find here. It's never a bad idea to learn more about computers since we all use them and that is a valuable skill in life too.
Re: general: computer/tech whizzes
Since you mentioned programming and digital security, those are two good starts. For digital security, I'd recommend this site to start: https://www.allclearid.com/personal/resource-center/
That's a online identity protection service and they have a good blog with resources and basic info on security that is written in a way that even the average user can understand. That's going to get into not only the how to protect yourself sort of deal (which is always useful) but also into the whys and hows on how this stuff happens. Anyone into security is going to know something of how thieves think because that is key to protection. A big idea with security is to make it so you aren't an easy target. This is more on the personal side though, if you are going to need to look into security on a corporate side that's a more tricky beast, but as long as you know basic terms you should be okay for RP. Definitely good stuff to learn even if RP isn't involved since security is important.
As far as programming goes, keep in mind that HTML is programming, so you already have some basics. If your character uses specific programming languages, try and learn something about those. If there isn't anything specific, I'd advise to try and learn a bit about CSS. CSS is a nice addition to knowledge of HTML and can be useful to you and learning some basics on it will give you some more in depth knowledge on programming and how programmers have to think. Try just learning some basics on it and see if you can play around with tweaking some code for your journal or plurk layouts. That will give you a better idea of what your character does and it's good practical knowledge as well. Even stuff like changing around your color scheme teaches a bit about how the code works.
Good luck to you! It's a complex and vast topic, but at least there are some things that are good to learn that you'll find here. It's never a bad idea to learn more about computers since we all use them and that is a valuable skill in life too.