The Korea Communications Commission warned Tuesday against malicious messages or spam being added on Google Calendar, the search engine’s schedule management service.

The Internet regulator urged users to reset their functions for the Calendar to block further attempts by hackers or marketers from sending unsolicited messages.

“Since the calendar service, by default, automatically accepts any invitations even by anonymous senders to share schedules, malicious files and links can be automatically listed on Google users’ mobile calendars,” a KCC official said.

For instance, if Google users click on events posted by spammers on their calendars, they could unknowingly be charged for opening full messages or advertisements.

The regulator recommended users to turn off the “Automatically add invitations to my calendar” option.

The KCC said it would work with Google to prevent mobile spam, which has been increasing with the use of time management applications.

Other mobile calendars such as Microsoft Outlook and Yahoo Calendar are also targeted by spammers and hackers implanting viruses or malicious codes on the services to retrieve personal information.

A market watcher said as spam and hacking attempts are becoming more sophisticated, mobile users should be cautious of opening mail or attachments from unknown sources.

He added that mobile calendar users should delete spam and ensure that they do not accept invites automatically.

By Kim Young-won (wone0102@heraldcorp.com)