You should disable automatic downloads in Chrome right now


Google Chrome end users on Home windows are suggested to disable automatic downloads in the website browser to guard authentication information against a new thread learned just lately.

The Chrome browser is the most well known browser proper now on desktop products. It is configured to obtain safe files immediately to the user method without the need of prompt by default.

Any file that Chrome end users obtain that passes Google’s safe searching checks will land in the default obtain listing immediately. Chrome end users who want to pick the obtain folder alternatively for downloads will need to alter that actions in the options.

The new attack, explained in detail on the Defense Code web site, brings together Chrome’s automatic obtain actions with Home windows Explorer Shell Command File files that have the .scf file extension.

The growing old structure is a basic textual content file that involves instructions, ordinarily an icon locale and limited commands. What is notably fascinating about the structure is that it might load methods from a remote server.

Even far more problematic is the simple fact that Home windows will system these files as shortly as you open the listing they are saved in, and that these files seem without the need of extension in Home windows Explorer irrespective of configurations. This implies that attackers could conveniently disguise the file behind a disguised filename these types of as graphic.jpg.

The attackers use a SMB server locale for the icon. What happens then is that the server requests authentication, and that the method will supply that.  Even though password hashes are submitted, the researchers take note that cracking those people passwords need to not consider a long time any longer until they are of the sophisticated type.

Concerning password cracking feasibility, this enhanced drastically in the earlier couple yrs with GPU-centered cracking. NetNTLMv2 hashcat benchmark for a one Nvidia GTX 1080 card is about 1600 MH/s. Which is 1.6 billion hashes for every second. For an eight-character password, GPU rigs of 4 these types of playing cards can go by means of an complete keyspace of higher/decrease alphanumeric + most typically utilised particular people (!@#$%&) in less than a working day. With hundreds of hundreds of thousands leaked passwords resulted from many breaches in the earlier yrs (LinkedIn, Myspace), wordlist rule-centered cracking can develop stunning outcomes against sophisticated passwords with far more entropy.

The condition is even worse for end users on Home windows eight or 10 equipment who authenticate with a Microsoft account, as the account will supply the attacker with accessibility to on the net products and services these types of as Outlook, OneDrive, or Office365 if utilised by the user. There is also the opportunity that the password is reused on non-Microsoft web pages.

Antivirus methods are not flagging these files proper now.

Below is how the attack goes down

  1. Consumer visits a web site which either pushes a travel by obtain to the user method, or receives the user to click on a specifically prepared SCF file so that it receives downloaded.
  2. Consumer opens the default obtain listing.
  3. Home windows checks the icon locale, and sends authentication information to the SMB server in hashed structure.
  4. Attacks might use password lists or brute drive assaults to crack the password.

How to guard your method against this attack

Just one choice that Chrome end users have is to disable automatic downloads in the website browser. This prevents travel by downloads, and might also protect against accidental downloads of files.

  1. Load chrome://configurations/ in the browser’s tackle bar.
  2. Scroll down and click on the “exhibit highly developed configurations” link.
  3. Scroll down to the Downloads portion.
  4. Look at the preference “Request the place to help save just about every file prior to downloading”.

Chrome will prompt you for a obtain locale just about every time a obtain is initiated in the browser.


Even though you increase a layer of safety to Chrome’s handling of downloads, manipulated SCF files might land in various methods on concentrate on programs.

Just one choice that end users and directors have is to block ports utilised by SMB targeted traffic in the firewall. Microsoft has a information up that you might use for that. The corporation indicates to block communication from and to the Online to the SMB ports 137, 138, 139 and 445.

Blocking these ports might have an impact on other Home windows products and services having said that these types of as the Fax services, print spooler, web logon, or file and print sharing.

Now You: How do you guard your equipment against SMB / SCF threats?

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The post You need to disable automatic downloads in Chrome proper now appeared very first on gHacks Engineering News.