The two companies have signed on with Western Union and the African Development Bank to head a new effort to aid victims of the attacks and help catch the perpetrators.
Lottery scams often reach users in the form of spam messages. The user is told that they have won a special internet lottery, and are then advised that to claim the prize and securely conduct the transaction, bank details must be provided.
The account information is then harvested by the attacker and sold or used for fraudulent transactions.
The campaign will establish a new service that allows victims of the scams to share police reports. The companies have set up web sites and email addresses through which users can contribute their reports to a database.
The hope is that the database will better enable both the companies and law enforcement agencies to link the lottery scam cases and track down the criminals behind the frauds. Interpol will also contribute to the project by spreading awareness of the site and encouraging law enforcement groups to utilise the database in investigations.
"At Yahoo, we've long told our users that if it sounds too good to be true, it probably is. But as internet fraudsters continue to get more creative in their approaches, consumers continue to be deceived," said George Hadjigeorgiou, Yahoo's European general manager of communication and community products.
"This unique initiative is a continuation of our online safety and trust initiatives and is intended to help support our consumer awareness efforts."