Keep software up to date
It may seem obvious, but ensuring you keep all software up to date is vital in keeping your site secure. This applies to both the server operating system and any software you may be running on your website such as a CMS or forum. When website security holes are found in software, hackers are quick to attempt to abuse them.
If you are using a managed hosting solution then you don’t need to worry so much about applying security updates for the operating system as the hosting company should take care of this.If you are using third-party software on your website such as a CMS or forum, you should ensure you are quick to apply any security patches. Most vendors have a mailing list or RSS feed detailing any website security issues. WordPress, Umbraco and many other CMSes notify you of available system updates when you log in.
SQL injection attacks are when an attacker uses a web form field or URL parameter to gain access to or manipulate your database. When you use standard Transact SQL it is easy to unknowingly insert rogue code into your query that could be used to change tables, get information and delete data. You can easily prevent this by always using parameterised queries, most web languages have this feature and it is easy to implement.
Consider this query:
“SELECT * FROM table WHERE column = ‘” + parameter + “‘;”
If an attacker changed the URL parameter to pass in ‘ or ‘1’=’1 this will cause the query to look like this:
“SELECT * FROM table WHERE column = ” OR ‘1’=’1′;”
Since ‘1’ is equal to ‘1’ this will allow the attacker to add an additional query to the end of the SQL statement which will also be executed.
Cross site scripting(XSS)
Server side validation/form validation
Validation should always be done both on the browser and server side. The browser can catch simple failures like mandatory fields that are empty and when you enter text into a numbers only field. These can however be bypassed, and you should make sure you check for these validation and deeper validation server side as failing to do so could lead to malicious code or scripting code being inserted into the database or could cause undesirable results in your website.
Everyone knows they should use complex passwords, but that doesn’t mean they always do. It is crucial to use strong passwords to your server and website admin area, but equally also important to insist on good password practices for your users to protect the security of their accounts.
As much as users may not like it, enforcing password requirements such as a minimum of around eight characters, including an uppercase letter and number will help to protect their information in the long run.
Passwords should always be stored as encrypted values, preferably using a one way hashing algorithm such as SHA. Using this method means when you are authenticating users you are only ever comparing encrypted values. For extra website security it is a good idea to salt the passwords, using a new salt per password.
Allowing users to upload files to your website can be a big website security risk, even if it’s simply to change their avatar. The risk is that any file uploaded however innocent it may look, could contain a script that when executed on your server completely opens up your website.
If you have a file upload form then you need to treat all files with great suspicion. If you are allowing users to upload images, you cannot rely on the file extension or the mime type to verify that the file is an image as these can easily be faked. Even opening the file and reading the header, or using functions to check the image size are not full proof. Most images formats allow storing a comment section which could contain PHP code that could be executed by the server.
SSL is a protocol used to provide security over the Internet. It is a good idea to use a security certificate whenever you are passing personal information between the website and web server or database. Attackers could sniff for this information and if the communication medium is not secure could capture it and use this information to gain access to user accounts and personal data.
Website security tools
Once you think you have done all you can then it’s time to test your website security. The most effective way of doing this is via the use of some website security tools, often referred to as penetration testing or pen testing for short.
There are many commercial and free products to assist you with this. They work on a similar basis to scripts hackers will use in that they test all know exploits and attempt to compromise your site using some of the previous mentioned methods such as SQL injection.