Several vendors offer computer programs designed to assist businesses in lead generation. Ethics are an important consideration in the choice and implementation of such programs. The use of spyware, Trojans or other intrusive means of gathering information without the knowledge or consent of targeted individuals or entities is frowned upon. Mass unsolicited e-mail advertising (or spam) is also considered unethical by many, and it can result in electronic blacklisting.
Leads may come from various sources or activities, for example, digitally via the Internet, through personal referrals, through telephone calls either by the company or telemarketers, through advertisements, and events. A 2015 study found that 89% of respondents cited email as the most-used channel for generating leads, followed by content marketing, search engine, and finally events. A study from 2014 found that direct traffic, search engines, and web referrals were the three most popular online channels for lead generation, accounting for 93% of leads.