Evernote, the software firm with an app designed for notetaking and archiving, is the latest to be hit by a distributed denial of service (DDoS) attack.
The software supports a number of operating platforms, including Apple's OS X and iOS, Google's Chrome OS and Android, as well as Windows and BlackBerry.
The firm, which claims that it has more than 100 million users, took to Twitter to state that it was struck by a DDoS attack, which started on Tuesday.
"We're actively working to neutralise a denial of service attack. You may experience problems accessing your Evernote while we resolve this," it said.
The attack left some members unable to synchronise files from one device to another.
In an update on Twitter, Evernote said that its service was back "up and running", but warned that "there may be a hiccup or two for the next 24 hours".
DDoS attacks can be costly for businesses in terms of lost revenue, the need to invest in new cyber defences, and in some cases potential extortion fees. Quite often, the attacks are most costly for their use as a decoy for other assaults.
A recent study by analytics provider Neustar found that a third of UK companies estimated losses of more than £240,000 per day as a result of DDoS attacks.
Despite this, the Cabinet Office went ahead with a trial of the software as part of an experiment with consumer laptops, tablets and other software.
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