Watching foreign movies clouds the mental and ideological health of the people.
Foreign hairstyles and clothing are signs of the "utterly rotten bourgeois lifestyle."
Shaking hands should be avoided in favour of bowing, as it is more hygienic and a part of the national culture.
For decades North Koreans have been forced to attend such sessions to reinforce the national illusion that they are lucky to live under the wise leadership of first Kim Il-sung, the nation's founder, and his son, Kim Jong-il, who inherited power after his father's died in 1994.
More than 100 pages of written lectures smuggled out of North Korea this year reveal that the leadership is in a state of near hysteria about outside influences seeping into the nation's once hermetically sealed borders.
The spread of "unusual lifestyles", the lectures warn listeners, could render them "incapable of following revolutionary thoughts and sacrificing their lives" for Kim Jong-il.
The documents also stress the extent of anti-Americanism. More than 50 years after the Korean War ended, the US is blamed for all of North Korea's woes, from food shortages to the infiltration of foreign culture.
"The bastards' indecent methods are clouding the mental and ideological health of the people," one lecture says.
"If we cannot stop them in time we will be in the same position as the Iraqis."
detected an air of desperation in the material.
North Korea takes extraordinary measures to inoculate its citizens against knowledge of the outside world. Radios and televisions are preset to government stations; foreign newspapers, magazines, books, films and music are banned.
But in recent years trade between North Korea and China has surged, often without the approval of North Korea's leaders. Along with food and consumer goods, traders smuggle in DVDs, tapes, books and Bibles, radios and mobile phones. T-shirts with English lettering, once considered taboo, are pouring into North Korean markets from Chinese garment factories.
The regime fears not only critical material but depictions of other nations that would make North Koreans realize how poor they are in comparison.
Lee Young-hwa, the head of Rescue the North Korean People, a human rights group based in Japan, which obtained the lectures, said they showed that North Koreans could not protect their borders from the entry of unwanted foreign materials.
"They cannot keep foreign material out," he said so all they can do is try to educate their people to resist."
Dr Myers said it was notable that the lectures did not urge people to report wrongdoers to police. "It's evident that even people in the party realise it is a losing battle to try to stem the influence of foreign culture."
"The enemies use these videos and specially made materials to beautify the world of imperialism and to spread a fantasy of the free world,” one lecture says.