State-run telecom service provider BSNL on Monday said it has taken swift action for reconfiguring the affected modems and restoring the broadband services of a few thousand subscribers across the country who were affected on July 25 by external virus attack on their modems.

The situation has "contained to a large extent and further efforts are on, to address the remaining complaints", it added.

"It is observed that, in the modems affected by attack, the "Internet" LED display of the modem turns to red colour, and Internet surfing was not happening. It has been identified that the attack is mostly limited to the modems for which the customers are continuing with the default "admin" password, and those which are associated with already infected computers/devices," the statement said.

"Customers are advised immediately to change the default modem password to their unique password, following best practices of setting passwords, so as to prevent virus attack into their modems," it added.

The statement added: "Instructions have been issued to all BSNL field units to educate all the customers about the procedures to configure their modems to prevent any vulnerability exploitation."