ARLINGTON, Va. ( TheStreet) -- ICx Technologies ( ICXT), one of the security technology stocks that soared the week after the Christmas holiday as a result of the attempted airline bombing, was the biggest gainer on Friday in the recently hot anti-terror stock category.

President Obama made it clear on Friday morning, in a press conference about the attempted bombing by the Nigerian terrorist, that the pressure is on the heads of his intelligence agencies to improve airport screening and other security measures. Janet Napolitano, the head of Homeland Security, spoke after President Obama's remarks and said it was premature to say how much the federal government would spend on airport security measures.

Shares of ICx ended Friday up 10.7%, for a gain of 87 cents to $8.97. While the one-day spike was notable, ICx is actually much lower than the 52-week high it hit the week after Christmas. And heavy selling earlier in the week kept its Friday gain from eclipsing the ICx level shares began trading at on Monday morning.

On Monday and Tuesday of this week, ICx experienced two consecutive days of more than 4 million shares traded, and closed below $8 on both days. ICx shares didn't rise above the $8 mark until Thursday. ICx shares' Friday volume of 3.3 million was well above its 1.1 million average, but still trailed the heavy trading at the beginning of the week.

During the post-holiday investor frenzy for homeland security-related technology stocks, ICx rose to a 52-week high of $10.49 on Dec. 31.

Anti-terror plays like ICx, as well as American Science & Engineering ( ASEI) and Implant Sciences ( IMSC), have become short-term momentum technology favorites. American Science ended Friday up a little more than 2%, or $1.71 to $83.53, though the company had attained a 52-week high during Friday's session above $84. American Science shares also cratered on Tuesday, with a decline of more than $6 from its current share price of $83.53.

However, both American Science and ICx are still way up from their share prices on Dec. 24. American Science was trading at $71 on the day before Christmas. ICx was trading at $4.98 on Christmas Eve.

Implant Sciences, albeit a tiny stock, has received a lot of play among anti-terror investors, but ended the day down more than 1.4%, to 34 and a half cents. Implant Sciences also saw its heaviest trading on Monday, when it shed almost half of its meager value.

OSI Systems ( OSIS) was the other big anti-terror winner on Friday, ending up close to 10%, or a gain of $2.75, to $31.64.

Unlike the other security technology stocks, which experienced heavy selling earlier in the week and recovered on Thursday and Friday, OSI shares saw their best trading on the last day of the week.

OSI shares were traded at volume above 3 million on Friday, versus an average of 656,000 shares traded. Three times as many OSI shares were traded on Friday as on any other day during 2010's first week. OSI also attained a 52-week high during Friday's session, but closed 79 cents below that Friday high level of $32.43.

-- Reported by Eric Rosenbaum in New York.

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