Several tech firms have urged people to change all their passwords after the discovery of a major security flaw called the Heartbleed Bug.
The Yahoo blogging platform Tumblr has advised the public to "change your passwords everywhere - especially your high-security services".
But with users told to pick a complicated, different log in for each site, trying to remember them all becomes a challenge.
Rory Cellan-Jones looks at some of the ways people can manage multiple strong passwords online.
