Recently, a client explained to me that he was unable to view Flash based content. He went on to say that he reinstalled Flash for Internet Explorer and Firefox. So I spent about three minutes trying the same thing thinking that he must have done something wrong. No luck, the normal “You must have Flash player installed….” message did not come up, but neither did the content.
After reviewing the issue with the client a little bit further, he explained that other users are having the same issue. Obviously, this isn’t a client computer / Flash issue.
I logged into the Sonicwall and checked the logs. Sure enough, the Sonicwall ran its daily IPS signature update and started blocking Flash. The really interesting thing is that we have pretty much no IPS configured, Sonicwall just deemed Flash unsafe. Keep an eye out for this, because if Flash “breaks” the last place you might look may be the firewall.
The IPS engine put this in the logs:
IPS Prevention Alert: MULTIMEDIA Shockwave Flash (SWF) Download 3, SID: 575, Priority: Low