Internet Explorer has anti-phishing settings which provide useful protection when browsing the wider web, but can also considerably slow down access to a heavily used intranet application like Koha when it is hosted off-site. These measures are called the Phishing Filter in Internet Explorer 7 and the SmartScreen Filter in Internet Explorer 8 and 9.
It is possible, but perhaps not advisable, to turn Phishing functions off, as this Microsoft support article on the Internet Explorer phishing filter explains.
A safer approach is to add the Koha website address to the list of “trusted sites” in your web browser to avoid the unnecessary and time consuming security check each time you visit a Koha web page, as this Microsoft support article on Internet Explorer trusted sites explains.
In some cases you may find that your browser settings are “locked down” to enforce corporate web browser policies and you are not able to change your browser settings yourself. In this case you will need to request your IT department to add the two Koha websites (the URLs of the OPAC and the Staff Client) - to the “trusted website list” of those browsers that require access to these sites.