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Archive for March 4th, 2020

Will You Put Your Password in a Survey?, (Thu, Mar 5th)

Thanks to one of our readers who submitted this interesting piece of phishing. Personally, I was not aware of this technique which is interesting to bypass common anti-spam filter and reputation systems. The idea is to create a fake survey on a well-known online service.

In this case, the attacker used surveygizmo.com[1] which offers you to build an online presence for surveys or feedback forms. Most of these websites are paid services but offer free trials. Enough to build a phishing campaign.

The generated link is sent to the victim as usual with some social engineering. Here is an example of the link:

hxxps://www[.]surveygizmo[.]com/s3/5485786/Invoice-4982550

The landing page looks like this:

(Note the typo “your o email”)

And, once you provided your credentials, the survey immediately ends with this screen:

The attacker just needs to login on his account to access data submitted by victims… You don’t need to deploy or hack a server to host the phishing page, you just use free resources provided by a cloud service. Pretty clever… And, if you’re ready to pay a small fee, you can even build self-branded surveys to increase the chances to lure victims.

[1] https://www.surveygizmo.com/

Xavier Mertens (@xme)
Senior ISC Handler – Freelance Cyber Security Consultant
PGP Key

(c) SANS Internet Storm Center. https://isc.sans.edu Creative Commons Attribution-Noncommercial 3.0 United States License.

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Let's Encrypt Revoking 3 Million Certificates, (Wed, Mar 4th)

Let’s Encrypt announced that they will be revoking a large number of certificates today. The revocation is due to an error in how “CAA” records were validated for these certificates.

The “CAA” (Certificate Authority Authorization) DNS record can be used to indicate which certificate authority is allowed to issue certificates for the particular domain or subdomain. For example, for DShield.org the record is:

% dig +short CAA dshield.org
0 iodef "mailto:[email protected]"
0 issue "letsencrypt.org"

This will allow “letsencrypt.org” to issue certificates, and the CA can notify [email protected] whenever it issues a certificate. 

Let’s Encrypt checked the CAA records whenever it validated domain ownership. But for Let’s Encrypt, domain ownership validation is good for 30 days. If you requested a new certificate within these 30 days, Let’s encrypt did not re-check the CAA record. CAA records are only supposed to be cached for up to 8 hrs.

Let’s Encrypt published a list of affected certificates [3]. You can search the list for domains you own. Let’s Encrypt also emailed the contact they had for the revoked certificates. They will be revoked today. Just as a precaution, you may want to check your site with SSLLabs or other test sides (good idea to do this from time to time 🙂 ).

[1] https://community.letsencrypt.org/t/revoking-certain-certificates-on-march-4/114864
[2] https://tools.ietf.org/html/rfc8659
[3] https://letsencrypt.org/caaproblem/


Johannes B. Ullrich, Ph.D. , Dean of Research, SANS Technology Institute
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(c) SANS Internet Storm Center. https://isc.sans.edu Creative Commons Attribution-Noncommercial 3.0 United States License.

Reposted from SANS. View original.

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