Beyond making sure all employees have up-to-date anit-virus software, the key advice from this article for SFDC customers: Salesforce offers… a powerful multi-factor authentication feature, which is offered by just 16% of cloud providers. When you have multi-factor authentication turned on, the first time a user accesses Salesforce.com from a computer using his username and password, he receives an SMS message with a code he must enter to gain access.