Your resume should be customized for each job you're interviewing for. The desired skill sets the employer is looking for should be listed on the top of your resume. Most people tend to put their most recent or best skills first, and that's OK. But it's better to put the requested skills on top where the hiring manager can see them.
If you're interested in the job, make sure you tell the interviewer you really want it. I've given many jobs to candidates who seemed highly interested in the job, even if they had a little less experience or qualifications than others. Follow-up emails and letters can't hurt, but don't stalk the interviewer. If they want you, they will call.
There's no secret to obtaining your first IT security job. Make the best of what you have. And if you don't have the necessary expertise, go get it. There are millions of pages about your desired skill set waiting to be read and downloaded off the Internet. Inventory your strengths and weaknesses, improve what you can, and go and get that job!
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