FUD（英語：Fear, Uncertainty, Doubt，意思為懼、惑、疑）最早指IBM销售人员對客戶灌輸阿姆達爾公司和其他競爭對手產品的負面觀念，在顾客的头脑中注入疑惑与惧怕，使顧客誤以為除了該公司的產品外，他們別無其他選擇。
最早出自吉恩·阿姆達爾之口，吉恩·阿姆達爾原為IBM工程師，之後離開IBM自行創立阿姆達爾公司，成為IBM競爭對手。
这种行销手法现在经常用于电脑业界，特別是微软常向客戶宣稱Linux與其他開放原始碼的軟體對客戶有弊無利。[1][2][3]
Burt, Thomas W.; Sparks, Bryan W. Settlement agreement - Microsoft Corporation and Caldera, Inc. reach agreement to settle antitrust lawsuit (PDF) (Court document). 2000-01-07 [2018-08-03]. Case 1:05-cv-01087-JFM, Document 104-8, Filed 2009-11-13; NOV00107061-NOV00107071; LT2288-LT2298; Lan12S311263739.1; Exhibit A. （原始内容存档 (PDF)于2017-07-04）. […] Microsoft will pay to Caldera, by wire transfer in accordance with written instructions provided by Caldera, the amount of two hundred eighty million dollars ($280,000,000), as full settlement of all claims or potential claims covered by this agreement […]
(NB. This document of the Caldera v. Microsoft case was an exhibit in the later Comes v. Microsoft case.) Wallis, Richard J.; Aeschbacher, Steven J.; Bettilyon, Mark M.; Webb, Jr., G. Stewar; Tulchin, David B.; Holley, Steven L. Microsoft's memorandum in opposition to Novell's renewed motion for summary judgement on Microsoft's affirmative defenses and in support of Microsoft's cross-motion for summary judgement (PDF) (Court document). United States District Court, District of Maryland: 16. 2009-11-13 [2018-08-03]. Novell, Inc. v. Microsoft Corporation, Civil Action No. JFM-05-1087. （原始内容存档 (PDF)于2019-05-24）. […] Microsoft paid $280 million to Caldera to settle the case […]
