I received an email which is classified as "potentially malicious" by my email program (Thunderbird), where links are actually a google URL query with extra parameters:

For example, the displayed text of the link is www.example.com/ but the actual link is https://www.google.com/url?q=http://www.example.com/&sa=D&ust=1535125407413000&usg=AFQjCNFsIVH5f4lBiIzr6njucxAoYFqy5A

I searched everywhere the meaning of those extra tags sa=, ust= and usg= but there is no official reference about it, and for example, the links provided in this answer seem outdated...

Also, I just noticed this is not a search, but an URL query (www.google.com/url?).

Is there something to worry about in this e-mail? Does anyone have an explanation of these URL parameters? How was this link made?

1 Answer 1


It is not a question of the parameters, but that the URL given in the links text and the real URL of the link point to different domains - which is a common technique in phishing mails.

To cite from Thunderbird’s Scam Detection:

Thunderbird's automatic scam filtering
It looks for characteristics in messages that are common in scam messages, for example:
Links where the text doesn't match the server name (for example, the text of the message might say "https://secure.example.com" but the link actually goes to "http://phishing.example.com" instead). Phishers do this to fool you into going to their site. Unfortunately some legitimate mailing lists also do this with redirectors for tracking purposes.

  • Yes I understood that, and then that led me to my question: should I worry about a seemingly harmless google URL? Can this type of URL be used as a phishing one? Sep 10, 2018 at 15:26
  • @PlasmaBinturong: In this specific case the URL is probably no problem since Google makes sure that this can not be used as a simple open redirect. Also, the link text actually describes where it is going correctly. But in general links which look like they are for a trusted domain but actually redirect to another can lead to successful phishing, as can do cases where the link text is for a different domain than the link target. In both cases the user might have trust into the target because the link text or target URL actually look familiar. Sep 10, 2018 at 15:56

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