re: Intrusion detection systems are security tools
This is not a letter. I don't know what it is. Is it an essay to be turned in for a grade? Is it "real life" writing for your job? Who is supposed to read it, and what is the purpose?
You need paragraphs.
Finally, give you threads meaningful titles please. Use a phrase from your post. Six threads all called "Help me with my letter" is not helpful.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.