Egan Orion the Inquirer, Thursday 8 November 2007. 09:32:00
Application signing mixup
A READER has been kind enough to pass on more information about the Leopard firewall's misinteraction with Skype, so we can supplement our previous story. It seems that when the firewall is active, it digitally signs third-party applications like Skype so it can later detect if they've been modified, like say, by a virus or other malware. The first time the application is loaded, a digital signature is appended to the program's executable. What happens then is not entirely clear, but the result in Skype's case is that subsequently the application doesn't run. Either Skype itself recognizes that the size of its binary file has changed, and refuses to run, or Mac OS/X 10.5 gets confused and refuses to run it, possibly because Skype might attempt to modify itself in memory, changing its own executable size....
http://rss1.mediafed.com/feed/vnunet...4dbf0c3e5a6da3

More...