SAN FRANCISCO — The Federal Election Commission said on Thursday that a Silicon Valley security company could immediately start helping 2020 presidential candidates defend their campaigns from the kinds of malicious email attacks that Russian hackers exploited in the 2016 election.

The F.E.C. made its advisory opinion one month after lawyers for the commission advised it to block a request by the company, Area 1 Security, which had sought to provide services to 2020 presidential candidates at a discount. The F.E.C. lawyers said that Area 1 would be violating campaign finance laws that prohibit corporations from offering free or discounted services to federal candidates. The same law also prevents political parties from offering candidates cybersecurity assistance because it is considered an “in-kind donation.”

The F.E.C.’s green light clears one major administrative roadblock that 2020 candidates faced as they sought assistance from Area 1 in defending against the attacks and disinformation campaigns that plagued 2016. The decision is limited to Area 1 because the company already offered similar services to other organizations at the same cost.

Cybersecurity and election specialists say time is running out for campaigns to develop the defenses capable of warding off attacks from sophisticated nation-state actors like Russia and others. In April, Christopher A. Wray, the F.B.I. director, warned that Russian election interference continued to pose a “significant counterintelligence threat” and that Russian efforts in the 2016 and 2018 elections were just “a dress rehearsal for the big show in 2020.”