The following numbers are usually blocked:

• Callers who do not respect the requisite level of transparency (purpose of call, company name, phone number, etc. not displayed)
• Callers who ignore the asterisk system in directories
• Callers who call at inappropriate hours (before 8 am or after 8:30 pm on weekdays, before 9 am or after 4 pm on Saturdays, or on Sundays and public holidays).
• Callers who call a customer more than once within a day
• Aggressive marketing calls (e.g. dubious sales tactics)
• Calls from numbers with an invalid format
• Numbers that many Swisscom customers have placed on their individual blacklists
• Numbers that many customers have designated as unwanted

The Callfilter does not usually block the following numbers:

• Calls that adhere to the code of conduct of the industry association for call centres (CallNet.ch), including respect for the asterisk system and no calls at inappropriate hours.
• Calls from serious survey institutes which adhere to industry standards and are not advertising calls
• Calls from official bodies such as the Federal Statistical Office
• Calls from firms which contact their customers using different numbers than those used for advertising calls