Website security is a massive concern to companies and also programmers. Hackers are becoming smarter and finding new vulnerabilities in the code of websites that will allow them access to sensitive data.
There are many ways in which you can try and protect your site from being compromised but nothing is 100% guaranteed, which is why it is vital to ensure you back up your website regularly.
Always make sure that you are using up to date versions of all plug-ins, external scripts and content management systems as often an update will contain fixes to known security issues.
Sites can not only be hacked by external sources as it can sometimes be ex employees or subcontractors. It is vital to change passwords when someone leaves and it is advisable to do this on a regular basis anyway.
Your programmer should be aware of how to make your site secure and if you are in any doubt do not hesitate to ask.