On 9/10/2020 7:37 AM, Hendrik Boom wrote:
On Thu, Sep 10, 2020 at 12:49:25AM -0400, George Neuner wrote:
>
> I don't know if DrRacket even sends a "user agent" string.
If DrRacket can send a user agent string, so can malware.
So it's not really reliable to filter on the user agent string.
-- hendrik
Of course ... any HTTP request can forge a user agent string: most
browsers allow you to change it, and so do some HTTP aware
applications. E.g., there is a plugin for Firefox that changes it on
the fly based on the URL - use cases involve things like Google image
search behaving differently for Chrome vs non-Chrome users, and
Microsoft sites behaving differently for non-Windows users.
My point is that there may be something unseen - probably a firewall -
blocking the DrRacket request but not blocking requests from the known
browser. If it isn't some software installed on the machine itself, it
likely is an IT appliance guarding the whole network. Firewall
appliances are NAT routers: they can look inside even encrypted
connections to examine protocols being used and the raw data passing
through.
Based on the error from Shriram's message, it looks like DrRacket is
successfully calling out but doesn't like/understand the response ...
which would tend to eliminate Windows built-in firewall as a suspect [it
doesn't do protocol inspection]. It still could be other AV/firewall
software on the machine, or something upstream in the network that his
student is unaware of.
YMMV,
George
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