SAN FRANCISCO — Hackers operating under the banner Anonymous have been poking a finger in the eye of one private company after another for two years now.

They steal files from inside corporate computer systems and occasionally, as in the case of Stratfor last week, dump company e-mail online for all to see.

The Stratfor hack, in which Anonymous claimed to have joined forces with WikiLeaks, drove home a clear lesson about the era of ubiquitous “hactivism,” or hacking as a form of protest.

Despite the arrests of dozens of suspected members of Anonymous and its offshoots worldwide, it is far from diminished. Nor have most of its corporate targets been irreparably damaged by the attacks.