About one in three (34%) free Wi-Fi hotspots block access to harmless websites, including sex education sites such as Respect Yourself, while a further 44% of them ban viewing of religious sites including Ikhwan Web, according to a new survey.
AdaptiveMobile's latest report revealed that over-blocking was worst in public spaces, with 66% of them prevented video streaming sites, with a third filtering sex education sites.
In addition, retail sites were also over-filtered, with 42% banning access to video streaming sites.
AdaptiveMobile Product Strategy and Business Development vice president Graeme Coffey said while it's encouraging that businesses have filters in place to protect users from inappropriate content, these results show a heavy-handed approach to filtering.
"Businesses offering free Wi-Fi are providing a service and if it's ineffective it could damage their reputation and make customers go elsewhere," Coffey said.
The security firm also revealed the 'hidden word problem' where web addresses were prevented by filters as the text comprised a series of letters being shared with an obscene phrase.
Over one third of websites including an inappropriate secret word, for instance the 'This is Scunthorpe' site, were banned, with 60% of sites being blocked by hotspots in public spaces.
AdaptiveMobile research also revealed that it was much more common for locations to seek personal details prior to accessing hidden word sites.
"These results show that a 'one size fits all approach' to Wi-Fi filtering clearly isn't working," Coffey added.
"We should apply the same rules to online as we do in real life. With filters becoming increasingly sophisticated and flexible this is now possible.
"Public outlets across the UK should review their Wi-Fi services and ensure they are fit for purpose."