He said it was unlikely that the siblings were acting alone. “That kind of information is useless unless you have an institutional or financial contact that has some interest in having it,” Mr. Marchetti said. “Them, alone, isolated without contacts is an unreasonable story. We should expect more worrying information to emerge, who actually took advantage of this information and who backed, supported or gave coverage to these operations.”

Italian observers noted that intelligence gathering for an advantage in, say, business or politics was not a new phenomenon here. “In the service of who or what and serving what end?” asked a columnist, Guido Gentili, in an editorial on Wednesday in the newspaper Il Sole 24 Ore. “The investigations will tell us but the impression remains that Italy once again is displaying, at the nexus of institutions, politics and business, one of its worst aspects: that of compiling dossiers, unauthorized surveillance and illegal collecting of private personal and professional information.”

Italian news media also noted Mr. Occhionero’s affiliation with Freemasonry. Several of the accounts that were violated belonged to fellow masons, and the hacking could have been motivated by an ambition to acquire positions within the organization, some newspapers suggested.

Some analysts went further, offering comparisons with the Propaganda Due, or P2, scandal involving a masonic lodge that in the 1970s gathered so much secret information and recruited so many top Italians officials that it was referred to as a “state within a state.”

Stefano Bisi, who is Grand Master of the Grand Orient of Italy, the country’s principal Masonic organization, said that “a lot of water had passed under the bridge” since the P2 scandal, and that in fact “masons were the victims” of Mr. Occhionero’s cyberattacks. Mr. Bisi was among those whose computers were hacked, but he said he could not imagine what Mr. Occhionero “could have been looking for.”

Mr. Occhionero denies any wrongdoing, his lawyer, Stefano Parretta, said Wednesday. He explained that his client had servers abroad “for business reasons,” and that the large box of files found in Mr. Occhionero’s garage were simply his company’s accounting books.

Ms. Occhionero’s lawyer, Roberto Bottachiari, told the Italian news agency ANSA that she “didn’t even know how to use a computer.”

Mr. Marchetti, the cybersecurity expert, said, “The idea of gathering information has happened in Italy many times before.” And on every occasion, “it highlights the dark side of that kind of world,” he said. “It’s worrying.”