Lockheed Corp. said it erected takeover defenses.

The Calabasas-based aerospace firm announced that its board of directors adopted a shareholder rights plan in which preferred stock rights will be distributed as a dividend at the rate of one right for each common share held as of the close of business on Dec. 22. Analysts said the move amounted to adoption of a “poison pill” defense against possible takeover. Lockheed stock rose sharply last month on rumors that the company was an acquisition target.