Malvertising Campaign Used a Free Certificate From Let's Encrypt (csoonline.com)

itwbennett writes: On Wednesday, Trend Micro wrote that it discovered a cyberattack on Dec. 21 that was designed to install banking malware on computers. The cybercriminals had compromised a legitimate website and set up a subdomain that led to a server under their control, wrote Joseph Chen, a fraud researcher with Trend. The subdomain used an SSL/TLS (Secure Sockets Layer/Transport Layer Security) certificate issued by Let's Encrypt, the first large-scale project to issue free digital certificates. which is run by the ISRG (Internet Security Research Group) and is backed by Mozilla, the Electronic Frontier Foundation, Cisco, and Akamai, among others. The incident has sparked disagreement over how to deal with such abuse, writes Jeremy Kirk.

Comments

Why the emphasis on Lets Encrypt?

[Richard_at_work]

This style of attack would have been able to get an SSL cert from most cheap cert providers, as most of the cheap ones only require you to dump a particular file in the right place on the website for verification, so why the emphasis on "Lets Encrypt"? Because they are "cheaper than cheap"?

Re:Why the emphasis on Lets Encrypt?

[QuietLagoon]

The emphasis on Let's Encrypt is misplaced.

.
Unlike most other CA's, Let's Encrypt has a very short lifetime on their certs (60 days, I believe) so that an abused cert quickly falls out of the eco-system. I've read that Let's Encrypt eventually wants to shorten that lifetime even more, to 30 days.

Most other CAs have cert lifetimes of a year (or longer). Then the question surfaces - how useful is cert revocation? Do all TLS clients check for cert revocation?

Re:Why the emphasis on Lets Encrypt?

[Anonymous Coward]

The lifetime at launch is actually 90 days (https://letsencrypt.org/2015/11/09/why-90-days.html)
The rest is correct.

Re:Why the emphasis on Lets Encrypt?

[Medievalist]

Most other CAs have cert lifetimes of a year (or longer). Then the question surfaces - how useful is cert revocation? Do all TLS clients check for cert revocation?

Most SSL/TLS clients do not check for a relevant CRL. The few that do (such as Firefox and other web browsers) typically require configuration and won't check for revocation by default out of the box.

In contrast, nearly all SSL/TLS clients that I am aware of (certain MTAs being an exception) will refuse to use an expired certificate unless specifically instructed to do so by the end user. So expiration is more likely to have an effect than revocation.

Re:Why the emphasis on Lets Encrypt?

[DarkOx]

If it is only a small part of data, that actually needs encryption â" the password and the credit card number â" you can do that (using the well-known and studied protocols) in JavaScript.

No you can't do that, no stop right right WRONG.

The JavaScript itself must be delivered on a authenticated encrypted channel because if it isn't how will my browser know its not supposed to run that XMLHttpRequest call to post a second plan text copy of that info to evil-hacker.com after you main in the middle my amazon session in the coffee shop.

Same goes with forms that are delivered over http but post https, this wrong and dangerous for the same reason. You can do authentication and encryption in the application layer if its a fat client and the client already has a static copy of trusted code form elsewhere but in the case of web site where the 'application' is being downloaded from the server the client needs a way authenticate and ensure transport integrity while obtaining the application itself otherwise its game over, your pwnd before you begin. The network layer is the correct place.

Inevitable

[The-Ixian]

I think that one way to deal with this would be in the browser.

Currently, EV certs will turn the address bar green or have some other indication above and beyond the normal "lock" icon.

Perhaps we need to have a different color or indication for each kind of cert.

Also, perhaps have a warning in the browser if the last known certificate is from a different CA and/or has a different validation level from the certificate currently being presented by the same domain.

Other than that, I am not sure what could be done on the server side of things. The system is meant to be free and open... which, by definition, means it is going to be abused.

Great Response

[Anonymous Coward]

This article looks like a really good response to the issue: https://unmitigatedrisk.com/?p=552

Why we cannot have nice things..

[wbr1]

The ISRG is both right and wrong. CAs cannot respond fast enough and likely do not have enough information to vet requests for new certificates fully. However, once a cert is used in bad faith it should be revoked.

The ad brokers do not care that bad ads slipped in as they make money on any, so they have zero incentive to remove malvertising other than a cursory effort to appease the lawyers and government.

This is why I install adblocks on all customer machines now (and we process a large amount). To an end user advertising of of limited utility, and comes with at minimum high annoyance and at worst malware/fraud/id theft.

Case in point, I was trying to find news information on a police standoff near my house, and one of the official local news stations ads were targeting nexus 6 with a scam 'free iPad' redirect. This only occurred on my Nexus 6, not a PC or LG phone. This is just normal day to day browsing, and I could not even read the news.

The state of affairs when it comes to online advertising and scams is very bad and will kill the industry very soon if changes are not made. Unfortunately it will likely bring down many good sites for real content with it.

Applies to All Non-EV Certificates

[EndlessNameless]

If they were able to create a subdomain, that means the attackers controlled all traffic to that subdomain.

Since most certificate authorities only verify via email to the domain for which the certificate is requested, the attackers would have gotten a certificate from virtually any CA.

There are additional verification steps required for EV certificates that should thwart this sort of attack, but singling out Let's Encrypt for issuing a certificate in this case is disingenuous.

The real problem lies with the DNS registrar that accepted an unauthorized subdomain registration request. (Or maybe the client's account was compromised, in which case the victim is to blame.)

Either way, the submission titles makes it seem this is a problem with Let's Encrypt when it most certainly is not.

NoScript, MITM of the crypto script, and Firesheep

[tepples]

If it is only a small part of data, that actually needs encryption — the password and the credit card number — you can do that (using the well-known and studied protocols) in JavaScript.

What you describe is similar to what Tloz proposes in the question "How to replace SSL/TLS?". But using client-side script to encrypt passwords has three drawbacks:

• It breaks on machines whose owners have configured them not to run JavaScript. But perhaps people who refuse to enable JavaScript can be filed with the "web sites ought to be static and apps ought to be native" extremists.
• It leaves the server hosting the script itself open to compromise by a man in the middle.
• Once the password is set, an HTTP cookie is normally set to mark subsequent HTTP requests as authenticated. But this leaves the site open to a "Firesheep"-style session cookie cloning attack.

DNS

[Stephen Chadfield]

This is just ridiculous. The problem here is that the attacker was able to create a new DNS sub-domain. The Let's Encrypt angle is just a red herring from a company (Trend Micro) that wants to make money selling SSL certificates.