It looks like #WannaCry’s killswitch check (www[.]iuqerfsodp9ifjaposdfjhgosurijfaewrwergwea[.]com) is not proxy aware:
Organizations that use proxies will not benefit from the killswitch.
Sample: 5ad4efd90dcde01d26cc6f32f7ce3ce0b4d4951d4b94a19aa097341aff2acaec
I have not tested this in a VM. If someone has, please post a comment with your findings.
Update: I did test the sample, it is not proxy aware. In an environment with an HTTP proxy and no direct connections to the Internet, the sample can not connect to www[.]iuqerfsodp9ifjaposdfjhgosurijfaewrwergwea[.]com, and it will infect the host.
If I patch the sample to make it proxy aware, it can connect to the site through the proxy, and it does not infect the host.
Didier Stevens 