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(Java.Trojan.ClassLoader.AI, JAVA/ClassLoad.AI.3,, Trojan.Downloader.Java.Openconnection.AJ, Exploit-ByteVerify, Trojan-Dropper.Java.Beyond.d, Java.Trojan.Femad.B, Trojan.Downloader.JAVA.Netlu.A, Trojan.Java.StartPage.f, Generic Dropper.g, JAVA_BYTEVER.AN,, Java.Trojan.ClassLoader.L, JAVA/BlackBox.AA.3, Trojan.Downloader.Java.Openstream.V, Trojan.Java.ClassLoader.v)

Added to the Dr.Web virus database: 2003-05-27

Virus description added:


Exploit.ByteVerify is a means of penetration into computers using the vulnerability in Microsoft Virtual Machine, build 5.0.3809 inclusive. The detailed description of this flaw in Microsoft’s software appeared in our news dated 09.04.2003.

The disclosure of the vulnerability and the patch release gave birth to a series of Trojan Horses, utilizing this exploit.

The computer becomes Trojan affected at simple viewing of a web-site with malicious Java-script embedded into it. Another way for them to tunnel into systems is to be executed by a user himself from HTML- attachment, received vi e-mail. An ill-intentioned Java-applet downloads from the internet and installs a Trojan program exploiting the ByteVerify vulnerability. Besides, the Trojan of this family can perform the following actions in the victimized machine:

  • it secures its automatic launch at every system startup
  • the Troj may considerably degrade the performance of Internet Explorer
  • when alphabetic symbols are typed into specified fields they will be displayed on the screen with some delay
  • if non-existing URL mistyped by a user or the address without www is entered into a search bar the default «Server is not found» page will not appear, instead, the browser will be redirected to a web-site determined in the Trojan’s code
  • links to dubious web-sites are added into Favourites folder
  • search bar is replaced
  • user stylesheet is replaced with Trojan’s own stylesheet file
  • when searching with Google, Yahoo, MSN and Altavista the Troj provoke multiple popup windows to show up
  • it can disguise its presence in a system as a driver update

Curing recommendations

  1. If the operating system (OS) can be loaded (either normally or in safe mode), download Dr.Web Security Space and run a full scan of your computer and removable media you use. More about Dr.Web Security Space.
  2. If you cannot boot the OS, change the BIOS settings to boot your system from a CD or USB drive. Download the image of the emergency system repair disk Dr.Web® LiveDisk , mount it on a USB drive or burn it to a CD/DVD. After booting up with this media, run a full scan and cure all the detected threats.
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Use Dr.Web Anti-virus for macOS to run a full scan of your Mac.

After booting up, run a full scan of all disk partitions with Dr.Web Anti-virus for Linux.

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  1. If the mobile device is operating normally, download and install Dr.Web for Android. Run a full system scan and follow recommendations to neutralize the detected threats.
  2. If the mobile device has been locked by Android.Locker ransomware (the message on the screen tells you that you have broken some law or demands a set ransom amount; or you will see some other announcement that prevents you from using the handheld normally), do the following:
    • Load your smartphone or tablet in the safe mode (depending on the operating system version and specifications of the particular mobile device involved, this procedure can be performed in various ways; seek clarification from the user guide that was shipped with the device, or contact its manufacturer);
    • Once you have activated safe mode, install the Dr.Web for Android onto the infected handheld and run a full scan of the system; follow the steps recommended for neutralizing the threats that have been detected;
    • Switch off your device and turn it on as normal.

Find out more about Dr.Web for Android