OPINION

On July 14, 2005, the District Court for the Eastern District of Pennsylvania imposed upon Appellant Allan Eric Carlson a sentence of 48 months imprisonment, a term of supervised release of three years, restitution of $14,970.63, and a special assessment of $7,900.00 after a jury found him guilty of computer and identification fraud in violation of 18 U.S.C. § 1030(a)(5)(A)(I) & (ii) (the “Computer Fraud and Abuse Act”) and 18 U.S.C. § 1028(a)(7)(the “Identity and Information Fraud Act”). 1 Carlson appeals the order denying his Fed.R.Crim.P. 29 motion for judgment of acquittal. The basis for his motion was insufficiency of the evidence brought against him under the Computer Fraud and Information Act. 2 We will affirm.

I.

This Court has jurisdiction to review the order of judgment in a criminal case pursuant to 28 U.S.C. § 1291. We exercise de novo review of the District Court’s denial of Carlson’s motion for judgment of acquittal. United States v. Flores, 454 F.3d 149, 154 (3d Cir. 2006).

II.

Prior to his arrest and conviction, Carlson was an avid Philadelphia Phillies fan living in California. (Appellant’s Brief, 2). He became savvy with internet use and technology in 1999, and in 2000 began posting messages on online bulletin boards devoted to the Philadelphia Phillies as a way to communicate with other Phillies fans. (JA 3.139-44).

Beginning in 2001, Carlson engaged in two types of e-mail activities that caused damage to other internet users: “direct attack” e-mailing, in which Carlson sent thousands of e-mails to one particular email address, 3 and “indirect attack” e-mailing, where he sent one e-mail to many email addresses. 4

*183 In employing the direct attack method, Carlson sent thousands of e-mails mainly to a few e-mail addresses at the Philadelphia Phillies. Although the ‘from’ field indicated that the e-mails were sent from various e-mail addresses not his own, 5 such as the FBI and the Philadelphia Phillies, they were not sent from those individuals and entities, but rather by Carlson using the Internet Protocol (“IP”) addresses of other computers. Carlson claims that he sent these e-mails in an attempt to inform journalists and Phillies management about issues with the management of the Phillies that he considered problematic, and to start conversations among other internet users concerning such problems. The evidence produced at trial showed that while some e-mails concerned the Phillies, others did not.

Examples of Carlson’s direct attacks are as follows. On November 7, 2001, Carlson sent 1,168 e-mails entitled “The Mariner’s Didn’t Trade A-Rod” from “Special [email protected],” an e-mail address belonging to a Canadian internet user, to six writers at Philadelphia Newspapers, Inc. (“PNI”). (JA 1.112, Supp.App. 4). On November 11, 2001, Carlson sent over 5,000 e-mails entitled “Sign JASON GIAMBI” to one address at the Phillies. (JA 2.107-113; Supp.App. 44-45). On March 12, Carlson sent 1,800 e-mails to one address at the Phillies, and another 1,800 e-mails to another Phillies’ address. (JA 2.115-7, 2.128-9; SuppApp. 44). On March 14, 2002, Carlson sent an e-mail entitled “The Color of Crime” about raced-based crimes to 5,514 employees of PNI. The e-mails appeared to be from either Lillian Swanson, Ombudsman of the Philadelphia Inquirer, or Walker Lundy, an editor of the Inquirer. (JA 1.143-15; Supp. App. 43, 49, 66-134).

When employing the indirect attack method, Carlson would send spam e-mails from spoofed accounts to thousands of people whose addresses he collected primarily by using computer software. 6 For example, On November 16, 2001, Carlson used the e-mail address of Greg Dubrow, a man with whom he had disagreements in conversations on an internet bulletin board. Carlson sent over 5,000 e-mails from Du-brow’s address to a Phillies address, as well as thousands of e-mails to other addresses, from which Dubrow received 6,000 returned e-mails. (JA 2.113; Supp. App. 44, 137-8). On November 19, 2001, Carlson spoofed the e-mail address of Paul Hagen, a sports writer at the Philadelphia Daily News, which caused 6,638 copies of this e-mail to be returned to Paul Hagen’s e-mail inbox. (JA, 1.125-127, 3.27-56; SuppApp., 43, 135,136). On April 9, 2002, Carlson sent thousands of e-mails from an address of a man who he claimed “stalked” him on the internet, 7,000 of which were returned as undeliverable to the alleged stalker’s inbox. (JA 2.78-82).

At trial, Carlson admitted to engaging in these activities, but denied that he knew that each time he employed the “indirect attack” method of e-mailing, it would result in a spoofed e-mailer’s receipt of hundreds of returned e-mails. 7 (JA 3.176-77). *184 He also denied intending to cause damage by sending thousands of e-mails to one email address, which would clog the address, result in delays, and at times require the purging of all e-mails, causing valuable business-related e-mails to be permanently lost. 8

The present appeal centers around whether the jury’s conviction of Mr. Carlson based upon the finding that he intended to cause damage when he sent e-mails, using both direct and indirect attacks, was supported by the evidence.

III.

We must view the sufficiency of the evidence claim 9 in the light most favorable to the Government, Wolfe, 245 F.3d at 261, and should sustain a verdict if “any rational trier of fact could have found the essential elements of the crime beyond a reasonable doubt.” United States v. Dent, 149 F.3d 180, 187 (3d Cir. 1998) (quoting United States v. Voigt, 89 F.3d 1050, 1080 (3d Cir. 1996)). A court, however, “must be ever vigilant in the context of Fed. R.Crim.P. 29 not to usurp the role of the jury by weighing credibility and assigning weight to the evidence, or by substituting its judgment for that of the jury.” Flores, 454 F.3d at 154. Accordingly, an appellant bears a “very heavy burden” to prove the evidence presented was insufficient to support the verdict. United States v. Gonzalez, 918 F.2d 1129, 1132 (3d Cir. 1990) (quoting United States v. Losada, 674 F.2d 167, 173 (2d Cir. 1982)).

The Computer Fraud and Abuse Act requires proof that a criminal defendant:

knowingly cause[d] the transmission of a program, information, code, or command, and as a result of such conduct, intentionally cause[d] damage without authorization, to a protected computer.

18 U.S.C. § 1030(a)(5)(A)(I)(emphasis added). Section 1030(e)(8) defines “damage” as “any impairment to the integrity or availability of data, a program, a system, or information.” Although the statute itself does not define “intentionally,” this Court has defined it in the criminal context as performing an act' deliberately and not by accident. United States v. Barbosa, 271 F.3d 438 (3d Cir. 2001). Accordingly, the Government was required to prove at trial that Carlson deliberately caused an impairment to the integrity or availability of data, a program, a system, or information.

The jury, after being properly charged as to both the elements of the crime and the definitions of relevant terms used therein, found that Carlson knowingly accessed a computer without authorization and intentionally caused damage thereto. Significantly, the District Court defined the meaning of intent as follows:

A person acts intentionally when what happens was the defendant’s conscious objective. To act intentionally means to do an act deliberately and not by acci *185 dent. The ultímate fact of intent, though subjective, may be established by circumstantial evidence based upon a person’s outward manifestations, his words, his conduct, his acts and all the surrounding circumstances disclosed by the evidence and the rational and logical inferences that may be drawn from them. To find the defendant guilty of Counts 1 through 26, you must find beyond a reasonable doubt that he intended to cause damage to the protected computer.

(JA 4.16, 9-19).

At trial, Carlson admitted that in using the direct e-mailing method and sending thousands of e-mails to one inbox, the targeted inbox would flood with e-mails and thus impair the user’s ability to access his other “good” e-mails. (JA 3.164-65). Carlson argued, however, that he only believed the targeted e-mail user’s ability to access his email would be impaired for a few minutes.

Carlson contended that, in employing the indirect e-mailing method, although he intentionally spoofed e-mail addresses from which he sent thousands of e-mails at a time, he did not intend that the consequence of this would be to flood the spoofed sender’s mailboxes with mail that was returned to sender and with replies requesting that the sender not e-mail the recipient in the future. (Appellant’s Brief, 2).

The testimony reflected, however, that Carlson was a sophisticated internet and email user. Carlson himself admitted to extensive knowledge of use of the internet and software, including knowledge of how to harvest e-mail addresses from websites, to send mass mailings, to use proxy servers, and to spoof e-mail addresses. (JA 3.151-156, 3.176-177). It is clear from the evidence that Carlson’s level of internet savvy, combined with his actions, could rationally be used as circumstantial evidence to conclude that Carlson intended the consequences of his actions.

TV.

We hold that sufficient evidence was presented at trial such that a reasonable juror could have found that Carlson, who intentionally accessed a computer without authorization, also intended the resultant damage. The Judgment of Conviction is affirmed.