what is the udev rule to allow specific vendor thumb drive?

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http://unix.stackexchange.com – i need a udev rule so that it should detect specific vendor and other pendrives it should not allow. how to write a rule and where we have to write the rule is it in /etc/udev/rules.d or /lib/udev/rules.d/ and what is the command to get effect of the udev rule. (HowTos)