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Linnea

A compiler for the Linnea query language.

Linnea can be used to find out which clients in a network are showing unusual request patterns.

Example Elephant:

{
	timestamp≥t0-2h,timestamp≤t0, 
	nxdomain, 
	match(domain,'^[a-f0-9]{8}\.(com|info|net)$^')
}, 
{
	[client| |suffix in 'com^','info','net':[client,d1 |d0=suffix]≥2| ]≥16
}

Which would read as:

  1. Select all NXDOMAINS that match a specific regex.
  2. Given this set, a client has to query at least 16 domains with at least two identical 2-strings for different suffixes.

And compile to:

SELECT dst, COUNT(dst) AS freq
FROM (
    SELECT request, dst, d0, d1, timestamp
    FROM (
        SELECT request, dst, d0, d1, timestamp,
            COUNT(((CASE WHEN (number_1 >= 1) THEN 1 ELSE 0 END)+(CASE WHEN (number_1 >= 1) THEN 1 ELSE 0 END)+(CASE WHEN (number_1 >= 1) THEN 1 ELSE 0 END)) >=  2 OR NULL) OVER(PARTITION BY dst ORDER BY timestamp RANGE BETWEEN INTERVAL '1 hour 0 minute' PRECEDING AND INTERVAL '1 hour 0 minute' FOLLOWING) AS number_0
        FROM (
            SELECT request, dst, d0, d1, timestamp,
                COUNT(d0 = 'com' OR NULL) OVER(PARTITION BY dst,d1 ORDER BY timestamp RANGE BETWEEN INTERVAL '1 hour 0 minute' PRECEDING AND INTERVAL '1 hour 0 minute' FOLLOWING) AS number_1
            FROM (
                SELECT request, dst, d0, d1, MAX(timestamp) AS timestamp
                FROM hplDNSReplies
                WHERE
                    timestamp >= (TIMESTAMP '2015-08-10 02:00:00') - INTERVAL '2 hour 0 minute'
                    AND timestamp <= (TIMESTAMP '2015-08-10 02:00:00')
                    AND (cat='NXDOMAIN')
                    AND (REGEXP_INSTR(request,'^[a-f0-9]{8}\.(com|info|net)$')>0
)
                GROUP BY dst, request, d0, d1
            ) layer_0
        ) layer_1
    ) layer_2
    WHERE number_0 >= 10
) layer_group
GROUP BY dst

Run Linnea

python linnea.py <grammar-file> <timestamp> <groupby> <execute> to run Linnea from the command line. Timestamp has to be of format YYYY-MM-DD HH:MM:SS, use quotes. If group by=1 (default), adds a surrounding aggregate that reduces the queries to client-wise. If connection values are set properly in the config.toml and execute=1 (default 0), then the query gets executed directly.

Language outline

  1. P_0,…,P_n defines the program, where each P_i is a predicate layer. Starting with P_0, the entirety of the domain data is fed into P_0, which yields the remaining domains, which will be fed into〖 P〗_1, and so forth until〖 P〗_n, which will be the output of the program.
  2. {p_0,…,p_n } defines a predicate set; it is true iff all predicates p_0,…,p_n are true. A predicate set forms a predicate layer.
  3. For Booleans and numbers, we have the usual arithmetic and logical operators.
  4. a=b is the string equality predicate.
  5. match(s,r) is true when the string s matches the regular expression r.
  6. count(s,r) counts the number of occurrences of the regular expression r in s.
  7. |g in h_0,…,h_n:p_i | counts how often the predicate p_i holds for each g∈{h_0,…,h_n }.
  8. g in h_0,…,h_n yields true iff i∈{h_0,…,h_n }.
  9. [a_0,…,a_n:T|p] finds in the current set of domain data those domains, that are in the timeframe [timestamp-T;timestamp+T] and have the same properties as the current domain, with respect to the property names a_0,…,a_n. It then counts given those how many fulfil the predicate p. These expressions are not allowed in P_0 for performance reasons.
  10. Various variables for each domain can be accessed, e.g. domain, client, timestamp, nxdomain, d0, l0.

More examples

Run python linnea.py examples/<dga>.linn to

{
	timestamp≥t_0-2h,timestamp≤t_0 
	nxdomain, 
	match(domain,'^[a-z]{5,12}\.(biz|com|info|net|org) $^')
}, 
{
	[client|true]≥25, 
	|i in 5,…,12:[client│l1=i]≥1|≥5,
	|suffix in 'com','biz','info','net','org': [client|d0=suffix]≥1|≥4,
	[client|l1=5 and d0  in 'com^','biz','info','net','org'] ≥1,  
	[client|l1=12 and d0  in 'com^','biz','info','net','org'] =0 
}

Which reads as:

  1. Select all NXDOMAINs that match a specific regex within the last two hours.
  2. Given this set, a client has to query at least 25 domains, at least 5 different 2-lengths, at least 4 different suffixes, at least one domain of length 5 with suffix com/info/net/org, and no domains of length 12 with suffix com/info/net/org.
{
	timestamp≥t_0-2h,timestamp≤t_0 
	nxdomain, 
	match(domain,'^[a-z]{11,23}\.com$^')
}, 
{
	[client|true]≥20, 
	[client|count(d_1 ,^'-')=1] ≥9,  
	[client│count(d_1 ,^'-')=2] ≥9 
}

Which reads as:

  1. Select all NXDOMAINS that match a specific regex.
  2. Given this set, a client has to query at least 25 domains, at least 20 domains containing exactly one hyphen, and at least 20 domains containing exactly 2 hyphens.