October 6, 2010 By Andrew Brandt

Patchy Phisher Forces Firefox to Forego Forgetting Passwords

Every browser can, at the user’s discretion, be set up to remember passwords. In general, Webroot advises most users not to set the browser to store login credentials, because they’re so easily extracted by password-stealing Trojans like Zbot. In Firefox, for example, you can click Tools, Options, then open the Security tab, and uncheck a box that tells the browser to remember passwords entered into Web forms. (The box is checked by default.)

But in the course of taking a more thorough look at a Trojan that came to our attention in July, we were surprised to see the Trojan modify a core Firefox file. Upon closer inspection, the Trojan patches a file named nsLoginManagerPrompter.js. The patch adds a few lines of code (displayed above), and comments-out other portions of code, that dictate whether Firefox prompts the user to save passwords when he or she logs into a secure site.

Before the infection, a default installation of Firefox 3.6.10 would prompt the user after the user clicks the Log In button on a Web page, asking whether he or she wants to save the password. After the infection, the browser simply saves all login credentials locally, and doesn’t prompt the user.

The keylogging Trojan copies itself to the system32 directory with the filename Kernel.exe; drops and registers an old, benign, deprecated ActiveX control called the Microsoft Internet Transfer Control DLL, or msinet.ocx (MD5: 7BEC181A21753498B6BD001C42A42722), which it uses to communicate with its command and control server; then it creates a new user account (username: Maestro) on the infected system.

The Trojan then scrapes information from the registry, from the so-called Protected Storage area used by IE to store passwords, and from Firefox’s own password storage, and tries to pass the stolen information onward, once per minute.

By the time we started researching the file by hand, the Web domain the Trojan tries to contact had been shut down. But there was a lot of other juicy information inside the Trojan.

For example, take a look at the following string embedded inside:

Well, pleased to meet you, Salar “Salixem” Zeynali. It’s not often you see a malware author taking credit for his creation using his real name. They’re usually a little smarter than that.

It didn’t take much effort to track down the author’s Facebook profile — he posts a link to it in his message board profile.

His Facebook profile indicates he lives in Karaj, Iran; He sports an emo haircut, and likes heavy metal music and programming. And, apparently, Zeynali writes crimeware for fun, because he doesn’t sell his keylogger. He offers a keylogger creator tool as a free download from the message board he hangs out on. Here’s a short list of some of the features included in one version.

Unfortunately, there are a lot of people who frequent the same message board Zeynali uses to post his keylogger code, and some of those people have clearly been using the keylogger creator tool Zeynali built to create and distribute Trojans. But there’s some good news: We’re able to easily identify and remove the Trojan (we call it Trojan-PWS-Nslog) from infected machines.

One thing that we, nor any other AV company, can do is fix the modified Firefox file. However, there’s an easy fix for that as well: Simply download the latest Firefox installer and install it over the top of your existing installation. You won’t lose any bookmarks or add-ons, and the installer will just overwrite the modified nsLoginManagerPrompter.js file. Problem solved.

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  1. […] virusschrijver zijn creatie met zijn eigen naam ondertekent. Ze zijn meestal iets slimmer", zegt Andrew Brandt van Webroot. Bron: security.nl […]

  2. […] whether he or she wants to save the password," Webroot researcher Andrew Brandt explained in a blog post on Wednesday. "After the infection, the browser simply saves all login credentials locally, […]

  3. […] he or she wants to save the password,” Webroot researcher Andrew Brandt explained in a blog post on Wednesday. “After the infection, the browser simply saves all login credentials locally, […]

  4. […] der Blog Webroot.com am 06.10.2010 berichtete wurde ein Trojaner entdeckt der die Passwörter im Firefox […]

  5. Il Trojan che ruba le password dal browser…

    Trojan-PWS-Nslog è il nome di una minaccia per i sistemi operativi Windows che si installa nella directory "System32" e crea un nuovo account utente, denominato "Maestro", attraverso il quale riesce a trafugare password da IE, Firef…

  6. […] is a very very serious issue ladies and gents, please click here to read the full article on this dangerous […]

  7. […] few lines of code are enough for Firefox to automatically save entered passwords. A trojan recently analysed by Webroot is said to rely on retrieving web page passwords from a browser’s password […]

  8. […] Mühe gemacht, unauffindbar zu bleiben. Denn hätte der iranische Entwickler ansonsten seinen Namen und seine Emailadresse im Code hinterlassen? Der Programmierer ist kein unbekannter im Virenbusiness und hat ebenfalls schon einen kostenlosen […]

  9. […] server; then it creates a new user account (username: Maestro) on the infected system,” points out one of the […]

  10. […] The webroot threat blog, who initially reported this several days ago, suggest installing the latest Firefox will fix the […]

  11. […] trojan recently analysed by Webroot is said to rely on retrieving web page passwords from a browser’s password […]

  12. […] Truva atı ve truva atını yapan kişi hakkında daha detaylı bilgilere ulaşmak isteyenleri şuraya alalım. Truva atının nsLoginManagerPrompter.js dosyasına eklediği kod yeşil renkle […]

  13. […] metode deductive? Perfect, atunci nu care cumva să citiți mai departeVirusologii de la Webroot au venit cu o descoperire interesantă: un mic Troian modifică lejer un fișier Firefox (nsLoginManagerPrompter.js), adaugă cîteva […]

  14. […] modifying Firefox to make password stealing more effective is relatively rare, but potentially very dangerous.  Malware authors have been experimenting with […]

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