Programs of prevention need to be properly designed and meet with international standards of best practice. To ensure respect for a program, whether it be on the part of employees or business partners, external verification is necessary. International best practices such as the Council for Further Combating Bribery of Foreign Public Officials in International Business Transactions, Annex 2; the ISO 26000 norm (section 6.6.3) or TI Business Principles for Countering Bribery are used in external verification processes to measure and ensure that a program of bribery prevention works and is consistent with international standards. Another reason for businesses to undergo external verification of their bribery prevention programs is that it means evidence can be provided to assert that all that was possible was done to prevent corruption. Companies are unable to guarantee corruption has never occurred; what they can do is provide evidence that they did their best to prevent it.