My firewall has detected and blocked an attack

[simonbrushfield]

Hi Studiopress,

I have just received about 30 email messages informing me that my firewall has detected and blocked an attack. The email message says...

Web Page: www.simonbrushfield.com/
Warning: URL may contain dangerous content!
Offending IP: 27.113.246.21 [ Get IP location ]
Offending Parameter: w3tc_referrer = http://www.google.com.au/url?sa=t&rc...s1PzwTmePF9DvQ

This may be a "WordPress-Specific SQL Injection Attack."

Click here for more information on this type of attack.

If you suspect this may be a false alarm because of something you recently did, try to confirm by repeating those actions. If so, whitelist it via the "whitelist this variable" link below. This will prevent future false alarms.

Click here to whitelist this variable.
Click here to turn off these emails.
Repeated warnings for similar attacks are currently sent via email, click here to suppress them."

How do I discover if it is a false alarm or serious and what should I do next?

Thanks,
Simon Brushfield
www.simonbrushfield.com