So, we have spent hell of a lot of time and money installing different systems but how we can be sure that everything done good? Once in the morning you can find out that top today news is: your company has been hacked! I think, you must get worst news first. For this purpose you can write own web robot but from my point of view the simplest way is google alert service. How we can use it?
Create a search pattern like " my_company_name hacked OR compromised OR defaced " change option How often to as-it-happens, provide email and vuala - once google find something it gonna inform you.
More over you can use google alert service for checking your company web-resources for occasional leakage of confidential information. For this purpose create pattern like "site:my_company_web_site.com confidential OR secret OR internal use" or special pattern for documents that should not be published "site:my_company_web_site.com confidential filetype:doc OR filetype:cad". So, google will monitor your web sites instead of you and notify you.
Sure thing you can combine both methods for control of private data leakage over the internet, finding negative information about your company, advertisement about selling your protected data, etc.
Keep informed! :-)