A hacking group that experts said was behind the sprawling ransomware attack that hit hours before the beginning of the July Fourth holiday weekend is demanding $70 million to unlock the thousands of businesses affected by the hack. REvil, the same Russian-language group that was behind the attack on meat processor JBS, posted the demand on a dark-Web site associated with the group. The group wants the funds in bitcoin, a popular cryptocurrency, and said if it receives the money it will publish a “decryptor key,” or a computer code that will unlock the victims’ files. The attack was carried out through software that helps businesses manage their computer systems, made by Miami-based firm Kaseya. Kaseya sells its tool to many large managed service providers, who in turn help small and midsize businesses monitor and control their computer networks.