Targeting Rogue and Opaque Letters Act of 2018 This bill makes sending bad faith patent demand letters an unfair or deceptive act in violation of the Federal Trade Commission Act. A patent demand letter is a written communication claiming that the recipient may be liable for patent infringement. "Bad faith" means making knowingly false or misleading statements, making claims with reckless disregard for the truth, or omitting information with the intent to deceive. Bad faith representations under the bill include false or misleading claims about the sender's right to assert the patent, whether lawsuits have been filed against the recipient or others, and whether others have purchased a license to exercise the patent. It is also bad faith to make written demands for compensation for invalid patents, or to demand compensation without identifying the ultimate parent entity of the letter sender. The sender has an affirmative defense that it acted in good faith, by proving its misstatements or omissions were unintentional and it made an error in spite of procedures to avoid such errors. The bill preempts state laws relating to patent assertion communications. The Federal Trade Commission and state attorneys general can bring actions to enforce these provisions.