text: Symantec says the Wifatch program is closing loopholes and fixing bugs on routers it infects.
  Routers are being increasingly targeted by criminals keen to steal data or to help with large-scale web attacks.
  Symantec has monitored the network of "vaccinated" devices but, so far, has not seen it put to malicious use.
  Wifatch was first discovered in late 2014 and since then has been steadily scouring the web for routers and other smart devices running vulnerable software.
  In a blogpost, Symantec said that once Wifatch finds and infects a vulnerable router it connects to other compromised devices to download software updates that make them harder to attack successfully.
  In addition, it said, Wifatch tries to disinfect devices that have been compromised by malicious software. It regularly reboots devices to kill off malware running on them and return them to a clean state.
  As far as Symantec can tell, Wifatch's payload has no malicious components and the growing network of compromised devices has never been used for attacks, said Symantec security analyst Mario Ballano.
  The software also leaves a message on the router telling its owner to change the default passwords and update the firmware that controls the device.
  Wifatch targets a wide variety of home routers that run variations of the Linux operating system. Symantec said that "tens of thousands" of gadgets were harbouring Wifatch. About a third of all the devices it had hit were in China with Brazil and Mexico making up another quarter of its victims.
  Symantec remained cautious about the intentions of Wifatch despite its benign appearance.
  "Wifatch is a piece of code that infects a device without user consent and, in that regard, is the same as any other piece of malware," said Mr Ballano.
  "It should also be pointed out that Wifatch contains a number of general-purpose back doors that can be used by the author to carry out potentially malicious actions," he added.
target: A benevolent virus has been used to harden more than 10,000 home routers against cyber-attacks, says a security firm.