Firefox certificate problem

[Bobke57]

When I try to connect to this URL: https://internetbanking.argenta.be/Argenta2/authenticationUCRNL.jsp
I get the following error message: "internetbanking.argenta.be:443 uses an invalid security certificate. The certificate is not trusted because the issuer certificate is unknown. (Error code: sec_error_unknown_issuer)"
Now I have connected to this website many times before, so the sudden change in behaviour worries me. I only upgraded the NoScript add-on in my Firefox 3.0.5 since, and I tried already disabling that. I have also waited a few days in case the problem is at the websites server, but the problem remains.
With Internet Explorer I can connect to this site without any problem.
How can I be sure that my Firefox is not hijacked or infected with malware? I did a scan with my Nod32 antivirus, and Spybot and Superantispyware, they all report tha my computer is clean.
The website provides a link to install the GlobalSign certificate they use, but how can I be sure this is legit? A rogue site might provide such a link too?
This is the website of my bank, so I don't want to risk to expose my password connecting to it.
I tried to export the GlobalSign certificate from my Internet Explorer, and import it to Firefox, but I get the message that it is already installed. Is it another certificate that I need to transfer?
I am using Vista SP1, Firefox 3.0.5, Internet Explorer 7.
Any help or advise is highly appreciated.

[JRViejo]

Bobke57, first, welcome to Wilders! I also get this Firefox error message:

206047

However, I have the Perspectives (http://www.cs.cmu.edu/~perspectives/) add-on installed in my FF 3.0.5 and a yellow bar, at the top of the page, informs me:

206048

So, I click on the Yes, contact Notaries button and the Web site is checked against a Certificate Key database to see if the site is legit. In this case it is and the page displays. You can further check by clicking on the Green Checkmark (bottom RH corner of browser) to see Perspectives' results:

206049

Click on the Certificates button, and one can see that it is a Temporary certificate:

206050

And when the View button is clicked, you can see the Certificate Viewer:

206051

I suggest installing the Perspectives add-on for this and any other Web site that requires server identification.

[Bobke57]

JRViejo, thank you very much for your reply.
That is a very interesting add-on that you have. I will install it also, as you suggest!
But, being a novice in this, and you seem to be very knowledgeable, allow me to ask you a few more questions so I can learn:
The fact that this certificate is temporary, does it mean it should not be trusted fully, so I should better not install the certificate in my Firefox? (If the organization is Argenta Spaarbank NV, it looks legit to me)
Do you know why Internet Explorer has no problems with this site, is it less strict than Firefox?
Thanks again!

[JRViejo]

-{ Quote: "The fact that this certificate is temporary, does it mean it should not be trusted fully, so I should better not install the certificate in my Firefox? (If the organization is Argenta Spaarbank NV, it looks legit to me)
Do you know why Internet Explorer has no problems with this site, is it less strict than Firefox?" }-
Bobke57, you're welcome! I trust Perspectives (yes, do install this add-on!) and although it's temporary, the certificate was issued by GlobalSign, plus the MD5 Fingerprint matches so I would trust it. Learn more about MD5 (http://en.wikipedia.org/wiki/MD5).

IMO, Firefox does a better job of handling security, via a myriad of add-ons, than IE. The fact that FF did not let you see the site first, because of a potential certificate problem, really exemplifies the difference between the two browsers. The Perspectives add-on is just icing on the cake, using a non-bias source to double check a site's certificate. Here's more info on Firefox Add-ons (https://addons.mozilla.org/en-US/firefox/?application=firefox) and look for the Most Popular section. NoScript and Adblock Plus are favorites of many Wilders members!

[Bobke57]

JRViejo, thanks for your explanation, which is most helpful !
Yes, I installed Perspectives yesterday. NoScript is one that I have already installed some time ago, and AdBlock was one that I was considering. But, since somehow I seem not to have so much problems with ads nor banners, I have not installed it yet.

[tlu]

An excellent overview about Firefox and certificates can be found here (http://www.h-online.com/security/The-right-way-to-handle-encryption-with-Firefox-3--/features/112797).