Once a police officer has properly detained a suspect for questioning, he may conduct a limited pat-down search of the suspect for weapons if he reasonably believes, based on specific and articulable facts, that the suspect might be armed and dangerous. See Phillips, 17 Va. App. at 30, 434 S.E.2d at 920. The officer need only "'reasonably believe that the individual might be armed.'" Lansdown v. Commonwealth, 226 Va. 204, 211, 308 S.E.2d 106, 111 (1983) (quoting Simmons v. Commonwealth, 217 Va. 552, 556, 231 S.E.2d 218, 220-21 (1977)), cert. denied, 465 U.S. 1104, 104 S. Ct. 1604, 80 L. Ed. 2d 134 (1984). The officer may rely upon the totality of the circumstances and may consider any suspicious actions of the person searched, such as an obvious attempt to avoid the officer or any nervous conduct based on the discovery of the officer's presence. See United States v. Bull, 565 F.2d 869, 870-71 (4th Cir. 1977), cert. denied, 435 U.S. 946, 55 L. Ed. 2d 545, 98 S. Ct. 1531 (1978). See also Williams v. Commonwealth, 4 Va. App. 53, 67, 354 S.E.2d 79, 87 (1987). "Frisking for weapons based upon the exigency of protecting an officer's safety is not limited to a pat-down of the suspect but may extend to nearby vehicles . . . or rooms or premises to which the suspect may retreat to secure a weapon." Washington v. Commonwealth, 29 Va. App. 5, 14, 509 S.E.2d 512, 516 (1999) (en banc). The Fourth Amendment does not require police to desist from effecting an otherwise valid Terry stop simply because the suspect moves from his porch to the living room through a still opened door. See Harbin v. City of Alexandria 712 F. Supp. 67, 72 (E.D.Va 1989). "If the suspect moves about, an officer is justified in staying with the individual during the course of the stop and conducting a protective search of the areas which come within the suspect's immediate control, even if this action necessitates entry into the suspect's home." Servis, 6 Va. App. at 519, 371 S.E.2d at 162. To conduct an investigatory stop of an individual, the police must possess reasonable suspicion based on articulable facts that the individual is, or has been, engaged in criminal activity. Terry v. Ohio, 392 U.S. 1, 21-22, 20 L. Ed. 2d 889, 88 S. Ct. 1868 (1968); Phillips v. Commonwealth, 17 Va. App. 27, 30, 434 S.E.2d 918, 920 (1993). "Anonymous information that has been sufficiently corroborated may furnish reasonable suspicion justifying an investigative stop." Bulatko v. Commonwealth, 16 Va. App. 135, 137, 428 S.E.2d 306, 307 (1993) (citing Alabama v. White, 496 U.S. 325, 331, 110 L. Ed. 2d 301, 110 S. Ct. 2412 (1990)). the independent corroboration gives "some degree of reliability to the other allegations" of the informant. Id.