Definition 

Negative screening excludes securities, often qualified as sin stocks, if the company activity is considered unethical or immoral, based on religious or philosophical views. Sin stock sectors usually include alcohol, tobacco, gambling, weapons, animal testing or pornography. 
Negative screening strategies can also refer to internationally accepted norms, such as the International Labor Organization standards, UN Global Compact, Universal Declaration of Human Rights and/or other globally recognized norms. This type of screening, called norm-based screening, is considered to be more objective, as the decisions to exclude sectors or companies are taken in accordance with standards established by international organizations.