Q. How do I find government articles on "Homeland Security?" How do I know the articles I find on the internet are valid?
You are right that articles you find on the web can be difficult to verify. One thing to check is the web address. If you are looking strictly for government publications you should look for the .gov at the end of the URL. You might try the site: http://www.usa.gov/ for your searches. All recent government publications are available freely online.
Another way to find valid/quality/scholarly articles on any topic is to use the library's databases. For this topic using "Military & Government Collection" where the search "homeland security" yields 17,000 results. Click the link below to access that database.
For more information on finding articles, including finding the full text, see the link below.